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CGI(3)                 Perl Programmers Reference Guide                 CGI(3)

       CGI - Simple Common Gateway Interface Class

         # CGI script that creates a fill-out form
         # and echoes back its values.

         use CGI qw/:standard/;
         print header,
               start_html('A Simple Example'),
               h1('A Simple Example'),
               "What's your name? ",textfield('name'),p,
               "What's the combination?", p,
                              -defaults=>['eenie','minie']), p,
               "What's your favorite color? ",

          if (param()) {
              my $name      = param('name');
              my $keywords  = join ', ',param('words');
              my $color     = param('color');
              print "Your name is",em(escapeHTML($name)),p,
                    "The keywords are: ",em(escapeHTML($keywords)),p,
                    "Your favorite color is ",em(escapeHTML($color)),

       This perl library uses perl5 objects to make it easy to create Web fill-out forms and parse their contents.
       This package defines CGI objects, entities that contain the values of the current query string and other state
       variables.  Using a CGI object's methods, you can examine keywords and parameters passed to your script, and
       create forms whose initial values are taken from the current query (thereby preserving state information).  The
       module provides shortcut functions that produce boilerplate HTML, reducing typing and coding errors. It also
       provides functionality for some of the more advanced features of CGI scripting, including support for file
       uploads, cookies, cascading style sheets, server push, and frames. also provides a simple function-oriented programming style for those who don't need its object-oriented

       The current version of is available at


       There are two styles of programming with, an object-oriented style and a function-oriented style.  In
       the object-oriented style you create one or more CGI objects and then use object methods to create the various
       elements of the page.  Each CGI object starts out with the list of named parameters that were passed to your
       CGI script by the server.  You can modify the objects, save them to a file or database and recreate them.
       Because each object corresponds to the "state" of the CGI script, and because each object's parameter list is
       independent of the others, this allows you to save the state of the script and restore it later.

       For example, using the object oriented style, here is how you create a simple "Hello World" HTML page:

          #!/usr/local/bin/perl -w
          use CGI;                             # load CGI routines
          $q = new CGI;                        # create new CGI object
          print $q->header,                    # create the HTTP header
                $q->start_html('hello world'), # start the HTML
                $q->h1('hello world'),         # level 1 header
                $q->end_html;                  # end the HTML

       In the function-oriented style, there is one default CGI object that you rarely deal with directly.  Instead
       you just call functions to retrieve CGI parameters, create HTML tags, manage cookies, and so on.  This provides
       you with a cleaner programming interface, but limits you to using one CGI object at a time.  The following
       example prints the same page, but uses the function-oriented interface.  The main differences are that we now
       need to import a set of functions into our name space (usually the "standard" functions), and we don't need to
       create the CGI object.

          use CGI qw/:standard/;           # load standard CGI routines
          print header,                    # create the HTTP header
                start_html('hello world'), # start the HTML
                h1('hello world'),         # level 1 header
                end_html;                  # end the HTML

       The examples in this document mainly use the object-oriented style.  See HOW TO IMPORT FUNCTIONS for important
       information on function-oriented programming in


       Most routines accept several arguments, sometimes as many as 20 optional ones!  To simplify this inter-
       face, all routines use a named argument calling style that looks like this:

          print $q->header(-type=>'image/gif',-expires=>'+3d');

       Each argument name is preceded by a dash.  Neither case nor order matters in the argument list.  -type, -Type,
       and -TYPE are all acceptable.  In fact, only the first argument needs to begin with a dash.  If a dash is
       present in the first argument, assumes dashes for the subsequent ones.

       Several routines are commonly called with just one argument.  In the case of these routines you can provide the
       single argument without an argument name.  header() happens to be one of these routines.  In this case, the
       single argument is the document type.

          print $q->header('text/html');

       Other such routines are documented below.

       Sometimes named arguments expect a scalar, sometimes a reference to an array, and sometimes a reference to a
       hash.  Often, you can pass any type of argument and the routine will do whatever is most appropriate.  For
       example, the param() routine is used to set a CGI parameter to a single or a multi-valued value.  The two cases
       are shown below:


       A large number of routines in actually aren't specifically defined in the module, but are generated
       automatically as needed.  These are the "HTML shortcuts," routines that generate HTML tags for use in dynami-
       cally-generated pages.  HTML tags have both attributes (the attribute="value" pairs within the tag itself) and
       contents (the part between the opening and closing pairs.)  To distinguish between attributes and contents, uses the convention of passing HTML attributes as a hash reference as the first argument, and the con-
       tents, if any, as any subsequent arguments.  It works out like this:

          Code                           Generated HTML
          ----                           --------------
          h1()                           <h1>
          h1('some','contents');         <h1>some contents</h1>
          h1({-align=>left});            <h1 align="LEFT">
          h1({-align=>left},'contents'); <h1 align="LEFT">contents</h1>

       HTML tags are described in more detail later.

       Many newcomers to are puzzled by the difference between the calling conventions for the HTML shortcuts,
       which require curly braces around the HTML tag attributes, and the calling conventions for other routines,
       which manage to generate attributes without the curly brackets.  Don't be confused.  As a convenience the curly
       braces are optional in all but the HTML shortcuts.  If you like, you can use curly braces when calling any rou-
       tine that takes named arguments.  For example:

          print $q->header( {-type=>'image/gif',-expires=>'+3d'} );

       If you use the -w switch, you will be warned that some argument names conflict with built-in Perl func-
       tions.  The most frequent of these is the -values argument, used to create multi-valued menus, radio button
       clusters and the like.  To get around this warning, you have several choices:

       1.  Use another name for the argument, if one is available.  For example, -value is an alias for -values.

       2.  Change the capitalization, e.g. -Values

       3.  Put quotes around the argument name, e.g. '-values'

       Many routines will do something useful with a named argument that it doesn't recognize.  For example, you can
       produce non-standard HTTP header fields by providing them as named arguments:

         print $q->header(-type  =>  'text/html',
                          -cost  =>  'Three smackers',
                          -annoyance_level => 'high',
                          -complaints_to   => 'bit bucket');

       This will produce the following nonstandard HTTP header:

          HTTP/1.0 200 OK
          Cost: Three smackers
          Annoyance-level: high
          Complaints-to: bit bucket
          Content-type: text/html

       Notice the way that underscores are translated automatically into hyphens.  HTML-generating routines perform a
       different type of translation.

       This feature allows you to keep up with the rapidly changing HTTP and HTML "standards".


            $query = new CGI;

       This will parse the input (from both POST and GET methods) and store it into a perl5 object called $query.


            $query = new CGI(INPUTFILE);

       If you provide a file handle to the new() method, it will read parameters from the file (or STDIN, or what-
       ever).  The file can be in any of the forms describing below under debugging (i.e. a series of newline delim-
       ited TAG=VALUE pairs will work).  Conveniently, this type of file is created by the save() method (see below).
       Multiple records can be saved and restored.

       Perl purists will be pleased to know that this syntax accepts references to file handles, or even references to
       filehandle globs, which is the "official" way to pass a filehandle:

           $query = new CGI(\*STDIN);

       You can also initialize the CGI object with a FileHandle or IO::File object.

       If you are using the function-oriented interface and want to initialize CGI state from a file handle, the way
       to do this is with restore_parameters().  This will (re)initialize the default CGI object from the indicated
       file handle.

           open (IN,"") || die;
           close IN;

       You can also initialize the query object from an associative array reference:

           $query = new CGI( {'dinosaur'=>'barney',
                              'song'=>'I love you',
                              'friends'=>[qw/Jessica George Nancy/]}

       or from a properly formatted, URL-escaped query string:

           $query = new CGI('dinosaur=barney&color=purple');

       or from a previously existing CGI object (currently this clones the parameter list, but none of the other
       object-specific fields, such as autoescaping):

           $old_query = new CGI;
           $new_query = new CGI($old_query);

       To create an empty query, initialize it from an empty string or hash:

          $empty_query = new CGI("");


          $empty_query = new CGI({});


            @keywords = $query->keywords

       If the script was invoked as the result of an <ISINDEX> search, the parsed keywords can be obtained as an array
       using the keywords() method.


            @names = $query->param

       If the script was invoked with a parameter list (e.g. "name1=value1&name2=value2&name3=value3"), the param()
       method will return the parameter names as a list.  If the script was invoked as an <ISINDEX> script and con-
       tains a string without ampersands (e.g. "value1+value2+value3") , there will be a single parameter named "key-
       words" containing the "+"-delimited keywords.

       NOTE: As of version 1.5, the array of parameter names returned will be in the same order as they were submitted
       by the browser.  Usually this order is the same as the order in which the parameters are defined in the form
       (however, this isn't part of the spec, and so isn't guaranteed).


           @values = $query->param('foo');


           $value = $query->param('foo');

       Pass the param() method a single argument to fetch the value of the named parameter. If the parameter is multi-
       valued (e.g. from multiple selections in a scrolling list), you can ask to receive an array.  Otherwise the
       method will return a single value.

       If a value is not given in the query string, as in the queries "name1=&name2=" or "name1&name2", it will be
       returned as an empty string.  This feature is new in 2.63.

       If the parameter does not exist at all, then param() will return undef in a scalar context, and the empty list
       in a list context.



       This sets the value for the named parameter 'foo' to an array of values.  This is one way to change the value
       of a field AFTER the script has been invoked once before.  (Another way is with the -override parameter
       accepted by all methods that generate form elements.)

       param() also recognizes a named parameter style of calling described in more detail later:



           $query->param(-name=>'foo',-value=>'the value');



       This adds a value or list of values to the named parameter.  The values are appended to the end of the parame-
       ter if it already exists.  Otherwise the parameter is created.  Note that this method only recognizes the named
       argument calling syntax.



       This creates a series of variables in the 'R' namespace.  For example, $R::foo, @R:foo.  For keyword lists, a
       variable @R::keywords will appear.  If no namespace is given, this method will assume 'Q'.  WARNING:  don't
       import anything into 'main'; this is a major security risk!!!!

       NOTE 1: Variable names are transformed as necessary into legal Perl variable names.  All non-legal characters
       are transformed into underscores.  If you need to keep the original names, you should use the param() method
       instead to access CGI variables by name.

       NOTE 2: In older versions, this method was called import().  As of version 2.20, this name has been removed
       completely to avoid conflict with the built-in Perl module import operator.



       This completely clears a list of parameters.  It sometimes useful for resetting parameters that you don't want
       passed down between script invocations.

       If you are using the function call interface, use "Delete()" instead to avoid conflicts with Perl's built-in
       delete operator.



       This clears the CGI object completely.  It might be useful to ensure that all the defaults are taken when you
       create a fill-out form.

       Use Delete_all() instead if you are using the function call interface.


       If POSTed data is not of type application/x-www-form-urlencoded or multipart/form-data, then the POSTed data
       will not be processed, but instead be returned as-is in a parameter named POSTDATA.  To retrieve it, use code
       like this:

          my $data = $query->param('POSTDATA');

       (If you don't know what the preceding means, don't worry about it.  It only affects people trying to use CGI
       for XML processing and other specialized tasks.)


          $q->param_fetch('address')->[1] = '1313 Mockingbird Lane';
          unshift @{$q->param_fetch(-name=>'address')},'George Munster';

       If you need access to the parameter list in a way that isn't covered by the methods above, you can obtain a
       direct reference to it by calling the param_fetch() method with the name of the .  This will return an array
       reference to the named parameters, which you then can manipulate in any way you like.

       You can also use a named argument style using the -name argument.


           $params = $q->Vars;
           print $params->{'address'};
           @foo = split("\0",$params->{'foo'});
           %params = $q->Vars;

           use CGI ':cgi-lib';
           $params = Vars;

       Many people want to fetch the entire parameter list as a hash in which the keys are the names of the CGI param-
       eters, and the values are the parameters' values.  The Vars() method does this.  Called in a scalar context, it
       returns the parameter list as a tied hash reference.  Changing a key changes the value of the parameter in the
       underlying CGI parameter list.  Called in a list context, it returns the parameter list as an ordinary hash.
       This allows you to read the contents of the parameter list, but not to change it.

       When using this, the thing you must watch out for are multivalued CGI parameters.  Because a hash cannot dis-
       tinguish between scalar and list context, multivalued parameters will be returned as a packed string, separated
       by the "\0" (null) character.  You must split this packed string in order to get at the individual values.
       This is the convention introduced long ago by Steve Brenner in his module for Perl version 4.

       If you wish to use Vars() as a function, import the :cgi-lib set of function calls (also see the section on
       CGI-LIB compatibility).



       This will write the current state of the form to the provided filehandle.  You can read it back in by providing
       a filehandle to the new() method.  Note that the filehandle can be a file, a pipe, or whatever!

       The format of the saved file is:


       Both name and value are URL escaped.  Multi-valued CGI parameters are represented as repeated names.  A session
       record is delimited by a single = symbol.  You can write out multiple records and read them back in with sev-
       eral calls to new.  You can do this across several sessions by opening the file in append mode, allowing you to
       create primitive guest books, or to keep a history of users' queries.  Here's a short example of creating mul-
       tiple session records:

          use CGI;

          open (OUT,">>test.out") || die;
          $records = 5;
          foreach (0..$records) {
              my $q = new CGI;
          close OUT;

          # reopen for reading
          open (IN,"test.out") || die;
          while (!eof(IN)) {
              my $q = new CGI(\*IN);
              print $q->param('counter'),"\n";

       The file format used for save/restore is identical to that used by the Whitehead Genome Center's data exchange
       format "Boulderio", and can be manipulated and even databased using Boulderio utilities.  See

       for further details.

       If you wish to use this method from the function-oriented (non-OO) interface, the exported name for this method
       is save_parameters().


       Errors can occur while processing user input, particularly when processing uploaded files.  When these errors
       occur, CGI will stop processing and return an empty parameter list.  You can test for the existence and nature
       of errors using the cgi_error() function.  The error messages are formatted as HTTP status codes. You can
       either incorporate the error text into an HTML page, or use it as the value of the HTTP status:

           my $error = $q->cgi_error;
           if ($error) {
               print $q->header(-status=>$error),
                     $q->h2('Request not processed'),
               exit 0;

       When using the function-oriented interface (see the next section), errors may only occur the first time you
       call param(). Be ready for this!


       To use the function-oriented interface, you must specify which routines or sets of routines to import
       into your script's namespace.  There is a small overhead associated with this importation, but it isn't much.

          use CGI <list of methods>;

       The listed methods will be imported into the current package; you can call them directly without creating a CGI
       object first.  This example shows how to import the param() and header() methods, and then use them directly:

          use CGI 'param','header';
          print header('text/plain');
          $zipcode = param('zipcode');

       More frequently, you'll import common sets of functions by referring to the groups by name.  All function sets
       are preceded with a ":" character as in ":html3" (for tags defined in the HTML 3 standard).

       Here is a list of the function sets you can import:

           Import all CGI-handling methods, such as param(), path_info() and the like.

           Import all fill-out form generating methods, such as textfield().

           Import all methods that generate HTML 2.0 standard elements.

           Import all methods that generate HTML 3.0 elements (such as <table>, <super> and <sub>).

           Import all methods that generate HTML 4 elements (such as <abbrev>, <acronym> and <thead>).

           Import all methods that generate Netscape-specific HTML extensions.

           Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' + 'netscape')...

           Import "standard" features, 'html2', 'html3', 'html4', 'form' and 'cgi'.

           Import all the available methods.  For the full list, see the code, where the variable %EXPORT_TAGS
           is defined.

       If you import a function name that is not part of, the module will treat it as a new HTML tag and gener-
       ate the appropriate subroutine.  You can then use it like any other HTML tag.  This is to provide for the
       rapidly-evolving HTML "standard."  For example, say Microsoft comes out with a new tag called <gradient> (which
       causes the user's desktop to be flooded with a rotating gradient fill until his machine reboots).  You don't
       need to wait for a new version of to start using it immediately:

          use CGI qw/:standard :html3 gradient/;
          print gradient({-start=>'red',-end=>'blue'});

       Note that in the interests of execution speed does not use the standard Exporter syntax for specifying
       load symbols.  This may change in the future.

       If you import any of the state-maintaining CGI or form-generating methods, a default CGI object will be created
       and initialized automatically the first time you use any of the methods that require one to be present.  This
       includes param(), textfield(), submit() and the like.  (If you need direct access to the CGI object, you can
       find it in the global variable $CGI::Q).  By importing methods, you can create visually elegant scripts:

          use CGI qw/:standard/;
              start_html('Simple Script'),
              h1('Simple Script'),
              "What's your name? ",textfield('name'),p,
              "What's the combination?",
              "What's your favorite color?",

           if (param) {
                  "Your name is ",em(param('name')),p,
                  "The keywords are: ",em(join(", ",param('words'))),p,
                  "Your favorite color is ",em(param('color')),".\n";
           print end_html;


       In addition to the function sets, there are a number of pragmas that you can import.  Pragmas, which are always
       preceded by a hyphen, change the way that functions in various ways.  Pragmas, function sets, and indi-
       vidual functions can all be imported in the same use() line.  For example, the following use statement imports
       the standard set of functions and enables debugging mode (pragma -debug):

          use CGI qw/:standard -debug/;

       The current list of pragmas is as follows:

           When you use CGI -any, then any method that the query object doesn't recognize will be interpreted as a new
           HTML tag.  This allows you to support the next ad hoc Netscape or Microsoft HTML extension.  This lets you
           go wild with new and unsupported tags:

              use CGI qw(-any);
              $q=new CGI;
              print $q->gradient({speed=>'fast',start=>'red',end=>'blue'});

           Since using <cite>any</cite> causes any mistyped method name to be interpreted as an HTML tag, use it with
           care or not at all.

           This causes the indicated autoloaded methods to be compiled up front, rather than deferred to later.  This
           is useful for scripts that run for an extended period of time under FastCGI or mod_perl, and for those des-
           tined to be crunched by Malcom Beattie's Perl compiler.  Use it in conjunction with the methods or method
           families you plan to use.

              use CGI qw(-compile :standard :html3);

           or even

              use CGI qw(-compile :all);

           Note that using the -compile pragma in this way will always have the effect of importing the compiled func-
           tions into the current namespace.  If you want to compile without importing use the compile() method

              use CGI();

           This is particularly useful in a mod_perl environment, in which you might want to precompile all CGI rou-
           tines in a startup script, and then import the functions individually in each mod_perl script.

           By default the CGI module implements a state-preserving behavior called "sticky" fields.  The way this
           works is that if you are regenerating a form, the methods that generate the form field values will interro-
           gate param() to see if similarly-named parameters are present in the query string. If they find a like-
           named parameter, they will use it to set their default values.

           Sometimes this isn't what you want.  The -nosticky pragma prevents this behavior.  You can also selectively
           change the sticky behavior in each element that you generate.

           Automatically add tab index attributes to each form field. With this option turned off, you can still add
           tab indexes manually by passing a -tabindex option to each field-generating method.

           This keeps from including undef params in the parameter list.

           By default, versions 2.69 and higher emit XHTML (  The -no_xhtml
           pragma disables this feature.  Thanks to Michalis Kabrianis <> for this feature.

           If start_html()'s -dtd parameter specifies an HTML 2.0 or 3.2 DTD, XHTML will automatically be disabled
           without needing to use this pragma.

           This makes produce a header appropriate for an NPH (no parsed header) script.  You may need to do
           other things as well to tell the server that the script is NPH.  See the discussion of NPH scripts below.

           Separate the name=value pairs in CGI parameter query strings with semicolons rather than ampersands.  For


           Semicolon-delimited query strings are always accepted, but will not be emitted by self_url() and
           query_string() unless the -newstyle_urls pragma is specified.

           This became the default in version 2.64.

           Separate the name=value pairs in CGI parameter query strings with ampersands rather than semicolons.  This
           is no longer the default.

           This overrides the autoloader so that any function in your program that is not recognized is referred to
  for possible evaluation.  This allows you to use all the functions without adding them to
           your symbol table, which is of concern for mod_perl users who are worried about memory consumption.  Warn-
           ing: when -autoload is in effect, you cannot use "poetry mode" (functions without the parenthesis).  Use
           hr() rather than hr, or add something like use subs qw/hr p header/ to the top of your script.

           This turns off the command-line processing features.  If you want to run a script from the command
           line to produce HTML, and you don't want it to read CGI parameters from the command line or STDIN, then use
           this pragma:

              use CGI qw(-no_debug :standard);

           This turns on full debugging.  In addition to reading CGI arguments from the command-line processing,
  will pause and try to read arguments from STDIN, producing the message "(offline mode: enter
           name=value pairs on standard input)" features.

           See the section on debugging for more details.

  can process uploaded file. Ordinarily it spools the uploaded file to a temporary directory, then
           deletes the file when done.  However, this opens the risk of eavesdropping as described in the file upload
           section.  Another CGI script author could peek at this data during the upload, even if it is confidential
           information. On Unix systems, the -private_tempfiles pragma will cause the temporary file to be unlinked as
           soon as it is opened and before any data is written into it, reducing, but not eliminating the risk of
           eavesdropping (there is still a potential race condition).  To make life harder for the attacker, the pro-
           gram chooses tempfile names by calculating a 32 bit checksum of the incoming HTTP headers.

           To ensure that the temporary file cannot be read by other CGI scripts, use suEXEC or a CGI wrapper program
           to run your script.  The temporary file is created with mode 0600 (neither world nor group readable).

           The temporary directory is selected using the following algorithm:

               1. if the current user (e.g. "nobody") has a directory named
               "tmp" in its home directory, use that (Unix systems only).

               2. if the environment variable TMPDIR exists, use the location

               3. Otherwise try the locations /usr/tmp, /var/tmp, C:\temp,
               /tmp, /temp, ::Temporary Items, and \WWW_ROOT.

           Each of these locations is checked that it is a directory and is writable.  If not, the algorithm tries the
           next choice.


       Many of the methods generate HTML tags.  As described below, tag functions automatically generate both the
       opening and closing tags.  For example:

         print h1('Level 1 Header');


         <h1>Level 1 Header</h1>

       There will be some times when you want to produce the start and end tags yourself.  In this case, you can use
       the form start_tag_name and end_tag_name, as in:

         print start_h1,'Level 1 Header',end_h1;

       With a few exceptions (described below), start_tag_name and end_tag_name functions are not generated automati-
       cally when you use CGI.  However, you can specify the tags you want to generate start/end functions for by
       putting an asterisk in front of their name, or, alternatively, requesting either "start_tag_name" or
       "end_tag_name" in the import list.


         use CGI qw/:standard *table start_ul/;

       In this example, the following functions are generated in addition to the standard ones:

       1. start_table() (generates a <table> tag)
       2. end_table() (generates a </table> tag)
       3. start_ul() (generates a <ul> tag)
       4. end_ul() (generates a </ul> tag)

       Most of's functions deal with creating documents on the fly.  Generally you will produce the HTTP header
       first, followed by the document itself. provides functions for generating HTTP headers of various types
       as well as for generating HTML.  For creating GIF images, see the module.

       Each of these functions produces a fragment of HTML or HTTP which you can print out directly so that it dis-
       plays in the browser window, append to a string, or save to a file for later use.


       Normally the first thing you will do in any CGI script is print out an HTTP header.  This tells the browser
       what type of document to expect, and gives other optional information, such as the language, expiration date,
       and whether to cache the document.  The header can also be manipulated for special purposes, such as server
       push and pay per view pages.

               print header;


               print header('image/gif');


               print header('text/html','204 No response');


               print header(-type=>'image/gif',
                                    -status=>'402 Payment required',

       header() returns the Content-type: header.  You can provide your own MIME type if you choose, otherwise it
       defaults to text/html.  An optional second parameter specifies the status code and a human-readable message.
       For example, you can specify 204, "No response" to create a script that tells the browser to do nothing at all.

       The last example shows the named argument style for passing arguments to the CGI methods using named
       parameters.  Recognized parameters are -type, -status, -expires, and -cookie.  Any other named parameters will
       be stripped of their initial hyphens and turned into header fields, allowing you to specify any HTTP header you
       desire.  Internal underscores will be turned into hyphens:

           print header(-Content_length=>3002);

       Most browsers will not cache the output from CGI scripts.  Every time the browser reloads the page, the script
       is invoked anew.  You can change this behavior with the -expires parameter.  When you specify an absolute or
       relative expiration interval with this parameter, some browsers and proxy servers will cache the script's out-
       put until the indicated expiration date.  The following forms are all valid for the -expires field:

               +30s                              30 seconds from now
               +10m                              ten minutes from now
               +1h                               one hour from now
               -1d                               yesterday (i.e. "ASAP!")
               now                               immediately
               +3M                               in three months
               +10y                              in ten years time
               Thursday, 25-Apr-1999 00:40:33 GMT  at the indicated time & date

       The -cookie parameter generates a header that tells the browser to provide a "magic cookie" during all subse-
       quent transactions with your script.  Netscape cookies have a special format that includes interesting
       attributes such as expiration time.  Use the cookie() method to create and retrieve session cookies.

       The -nph parameter, if set to a true value, will issue the correct headers to work with a NPH (no-parse-header)
       script.  This is important to use with certain servers that expect all their scripts to be NPH.

       The -charset parameter can be used to control the character set sent to the browser.  If not provided, defaults
       to ISO-8859-1.  As a side effect, this sets the charset() method as well.

       The -attachment parameter can be used to turn the page into an attachment.  Instead of displaying the page,
       some browsers will prompt the user to save it to disk.  The value of the argument is the suggested name for the
       saved file.  In order for this to work, you may have to set the -type to "application/octet-stream".

       The -p3p parameter will add a P3P tag to the outgoing header.  The parameter can be an arrayref or a space-
       delimited string of P3P tags.  For example:

          print header(-p3p=>[qw(CAO DSP LAW CURa)]);
          print header(-p3p=>'CAO DSP LAW CURa');

       In either case, the outgoing header will be formatted as:

         P3P: policyref="/w3c/p3p.xml" cp="CAO DSP LAW CURa"


          print redirect('http://somewhere.else/in/movie/land');

       Sometimes you don't want to produce a document yourself, but simply redirect the browser elsewhere, perhaps
       choosing a URL based on the time of day or the identity of the user.

       The redirect() function redirects the browser to a different URL.  If you use redirection like this, you should
       not print out a header as well.

       You should always use full URLs (including the http: or ftp: part) in redirection requests.  Relative URLs will
       not work correctly.

       You can also use named arguments:

           print redirect(-uri=>'http://somewhere.else/in/movie/land',

       The -nph parameter, if set to a true value, will issue the correct headers to work with a NPH (no-parse-header)
       script.  This is important to use with certain servers, such as Microsoft IIS, which expect all their scripts
       to be NPH.

       The -status parameter will set the status of the redirect.  HTTP defines three different possible redirection
       status codes:

            301 Moved Permanently
            302 Found
            303 See Other

       The default if not specified is 302, which means "moved temporarily."  You may change the status to another
       status code if you wish.  Be advised that changing the status to anything other than 301, 302 or 303 will prob-
       ably break redirection.


          print start_html(-title=>'Secrets of the Pyramids',
                                   -meta=>{'keywords'=>'pharaoh secret mummy',
                                           'copyright'=>'copyright 1996 King Tut'},

       After creating the HTTP header, most CGI scripts will start writing out an HTML document.  The start_html()
       routine creates the top of the page, along with a lot of optional information that controls the page's appear-
       ance and behavior.

       This method returns a canned HTML header and the opening <body> tag.  All parameters are optional.  In the
       named parameter form, recognized parameters are -title, -author, -base, -xbase, -dtd, -lang and -target (see
       below for the explanation).  Any additional parameters you provide, such as the Netscape unofficial BGCOLOR
       attribute, are added to the <body> tag.  Additional parameters must be proceeded by a hyphen.

       The argument -xbase allows you to provide an HREF for the <base> tag different from the current location, as in


       All relative links will be interpreted relative to this tag.

       The argument -target allows you to provide a default target frame for all the links and fill-out forms on the
       page.  This is a non-standard HTTP feature which only works with Netscape browsers!  See the Netscape documen-
       tation on frames for details of how to manipulate this.


       All relative links will be interpreted relative to this tag.  You add arbitrary meta information to the header
       with the -meta argument.  This argument expects a reference to an associative array containing name/value pairs
       of meta information.  These will be turned into a series of header <meta> tags that look something like this:

           <meta name="keywords" content="pharaoh secret mummy">
           <meta name="description" content="copyright 1996 King Tut">

       To create an HTTP-EQUIV type of <meta> tag, use -head, described below.

       The -style argument is used to incorporate cascading stylesheets into your code.  See the section on CASCADING
       STYLESHEETS for more information.

       The -lang argument is used to incorporate a language attribute into the <html> tag.  For example:

           print $q->start_html(-lang=>'fr-CA');

       The default if not specified is "en-US" for US English, unless the -dtd parameter specifies an HTML 2.0 or 3.2
       DTD, in which case the lang attribute is left off.  You can force the lang attribute to left off in other cases
       by passing an empty string (-lang=>'').

       The -encoding argument can be used to specify the character set for XHTML.  It defaults to iso-8859-1 if not

       The -declare_xml argument, when used in conjunction with XHTML, will put a <?xml> declaration at the top of the
       HTML header. The sole purpose of this declaration is to declare the character set encoding. In the absence of
       -declare_xml, the output HTML will contain a <meta> tag that specifies the encoding, allowing the HTML to pass
       most validators.  The default for -declare_xml is false.

       You can place other arbitrary HTML elements to the <head> section with the -head tag.  For example, to place
       the rarely-used <link> element in the head section, use this:

           print start_html(-head=>Link({-rel=>'next',

       To incorporate multiple HTML elements into the <head> section, just pass an array reference:

           print start_html(-head=>[

       And here's how to create an HTTP-EQUIV <meta> tag:

             print start_html(-head=>meta({-http_equiv => 'Content-Type',
                                           -content    => 'text/html'}))

       JAVASCRIPTING: The -script, -noScript, -onLoad, -onMouseOver, -onMouseOut and -onUnload parameters are used to
       add Netscape JavaScript calls to your pages.  -script should point to a block of text containing JavaScript
       function definitions.  This block will be placed within a <script> block inside the HTML (not HTTP) header.
       The block is placed in the header in order to give your page a fighting chance of having all its JavaScript
       functions in place even if the user presses the stop button before the page has loaded completely.
       attempts to format the script in such a way that JavaScript-naive browsers will not choke on the code: unfortu-
       nately there are some browsers, such as Chimera for Unix, that get confused by it nevertheless.

       The -onLoad and -onUnload parameters point to fragments of JavaScript code to execute when the page is respec-
       tively opened and closed by the browser.  Usually these parameters are calls to functions defined in the
       -script field:

             $query = new CGI;
             print header;
             // Ask a silly question
             function riddle_me_this() {
                var r = prompt("What walks on four legs in the morning, " +
                              "two legs in the afternoon, " +
                              "and three legs in the evening?");
             // Get a silly answer
             function response(answer) {
                if (answer == "man")
                   alert("Right you are!");
                   alert("Wrong!  Guess again.");
             print start_html(-title=>'The Riddle of the Sphinx',

       Use the -noScript parameter to pass some HTML text that will be displayed on browsers that do not have
       JavaScript (or browsers where JavaScript is turned off).

       Netscape 3.0 recognizes several attributes of the <script> tag, including LANGUAGE and SRC.  The latter is par-
       ticularly interesting, as it allows you to keep the JavaScript code in a file or CGI script rather than clut-
       tering up each page with the source.  To use these attributes pass a HASH reference in the -script parameter
       containing one or more of -language, -src, or -code:

           print $q->start_html(-title=>'The Riddle of the Sphinx',

           print $q->(-title=>'The Riddle of the Sphinx',
                                -code=>'print "hello world!\n;"'}

       A final feature allows you to incorporate multiple <script> sections into the header.  Just pass the list of
       script sections as an array reference.  this allows you to specify different source files for different
       dialects of JavaScript.  Example:

            print $q->start_html(-title=>'The Riddle of the Sphinx',
                                           { -language => 'JavaScript1.0',
                                             -src      => '/javascript/utilities10.js'
                                           { -language => 'JavaScript1.1',
                                             -src      => '/javascript/utilities11.js'
                                           { -language => 'JavaScript1.2',
                                             -src      => '/javascript/utilities12.js'
                                           { -language => 'JavaScript28.2',
                                             -src      => '/javascript/utilities219.js'

       If this looks a bit extreme, take my advice and stick with straight CGI scripting.


       for more information about JavaScript.

       The old-style positional parameters are as follows:

       1.  The title

       2.  The author's e-mail address (will create a <link rev="MADE"> tag if present

       3.  A 'true' flag if you want to include a <base> tag in the header.  This helps resolve relative addresses to
           absolute ones when the document is moved, but makes the document hierarchy non-portable.  Use with care!

       4, 5, 6...
           Any other parameters you want to include in the <body> tag.  This is a good place to put Netscape exten-
           sions, such as colors and wallpaper patterns.


               print end_html

       This ends an HTML document by printing the </body></html> tags.


           $myself = self_url;
           print q(<a href="$myself">I'm talking to myself.</a>);

       self_url() will return a URL, that, when selected, will reinvoke this script with all its state information
       intact.  This is most useful when you want to jump around within the document using internal anchors but you
       don't want to disrupt the current contents of the form(s).  Something like this will do the trick.

            $myself = self_url;
            print "<a href=\"$myself#table1\">See table 1</a>";
            print "<a href=\"$myself#table2\">See table 2</a>";
            print "<a href=\"$myself#yourself\">See for yourself</a>";

       If you want more control over what's returned, using the url() method instead.

       You can also retrieve the unprocessed query string with query_string():

           $the_string = query_string;


           $full_url      = url();
           $full_url      = url(-full=>1);  #alternative syntax
           $relative_url  = url(-relative=>1);
           $absolute_url  = url(-absolute=>1);
           $url_with_path = url(-path_info=>1);
           $url_with_path_and_query = url(-path_info=>1,-query=>1);
           $netloc        = url(-base => 1);

       url() returns the script's URL in a variety of formats.  Called without any arguments, it returns the full form
       of the URL, including host name and port number


       You can modify this format with the following named arguments:

           If true, produce an absolute URL, e.g.


           Produce a relative URL.  This is useful if you want to reinvoke your script with different parameters. For


           Produce the full URL, exactly as if called without any arguments.  This overrides the -relative and -abso-
           lute arguments.

       -path (-path_info)
           Append the additional path information to the URL.  This can be combined with -full, -absolute or -rela-
           tive.  -path_info is provided as a synonym.

       -query (-query_string)
           Append the query string to the URL.  This can be combined with -full, -absolute or -relative.
           -query_string is provided as a synonym.

           Generate just the protocol and net location, as in

           If Apache's mod_rewrite is turned on, then the script name and path info probably won't match the request
           that the user sent. Set -rewrite=>1 (default) to return URLs that match what the user sent (the original
           request URI). Set -rewrite->0 to return URLs that match the URL after mod_rewrite's rules have run. Because
           the additional path information only makes sense in the context of the rewritten URL, -rewrite is set to
           false when you request path info in the URL.


          $color = url_param('color');

       It is possible for a script to receive CGI parameters in the URL as well as in the fill-out form by creating a
       form that POSTs to a URL containing a query string (a "?" mark followed by arguments).  The param() method will
       always return the contents of the POSTed fill-out form, ignoring the URL's query string.  To retrieve URL
       parameters, call the url_param() method.  Use it in the same way as param().  The main difference is that it
       allows you to read the parameters, but not set them.

       Under no circumstances will the contents of the URL query string interfere with similarly-named CGI parameters
       in POSTed forms.  If you try to mix a URL query string with a form submitted with the GET method, the results
       will not be what you expect.

CREATING STANDARD HTML ELEMENTS: defines general HTML shortcut methods for most, if not all of the HTML 3 and HTML 4 tags.  HTML short-
       cuts are named after a single HTML element and return a fragment of HTML text that you can then print or manip-
       ulate as you like.  Each shortcut returns a fragment of HTML code that you can append to a string, save to a
       file, or, most commonly, print out so that it displays in the browser window.

       This example shows how to use the HTML methods:

          print $q->blockquote(
                            "Many years ago on the island of",
                            "there lived a Minotaur named",

       This results in the following HTML code (extra newlines have been added for readability):

          Many years ago on the island of
          <a href="">Crete</a> there lived
          a minotaur named <strong>Fred.</strong>

       If you find the syntax for calling the HTML shortcuts awkward, you can import them into your namespace and dis-
       pense with the object syntax completely (see the next section for more details):

          use CGI ':standard';
          print blockquote(
             "Many years ago on the island of",
             "there lived a minotaur named",


       The HTML methods will accept zero, one or multiple arguments.  If you provide no arguments, you get a single

          print hr;    #  <hr>

       If you provide one or more string arguments, they are concatenated together with spaces and placed between
       opening and closing tags:

          print h1("Chapter","1"); # <h1>Chapter 1</h1>"

       If the first argument is an associative array reference, then the keys and values of the associative array
       become the HTML tag's attributes:

          print a({-href=>'fred.html',-target=>'_new'},
             "Open a new frame");

                   <a href="fred.html",target="_new">Open a new frame</a>

       You may dispense with the dashes in front of the attribute names if you prefer:

          print img {src=>'fred.gif',align=>'LEFT'};

                  <img align="LEFT" src="fred.gif">

       Sometimes an HTML tag attribute has no argument.  For example, ordered lists can be marked as COMPACT.  The
       syntax for this is an argument that that points to an undef string:

          print ol({compact=>undef},li('one'),li('two'),li('three'));

       Prior to version 2.41, providing an empty ('') string as an attribute argument was the same as providing
       undef.  However, this has changed in order to accommodate those who want to create tags of the form <img
       alt="">.  The difference is shown in these two pieces of code:

          CODE                   RESULT
          img({alt=>undef})      <img alt>
          img({alt=>''})         <img alt="">


       One of the cool features of the HTML shortcuts is that they are distributive.  If you give them an argument
       consisting of a reference to a list, the tag will be distributed across each element of the list.  For example,
       here's one way to make an ordered list:

          print ul(

       This example will result in HTML output that looks like this:

            <li type="disc">Sneezy</li>
            <li type="disc">Doc</li>
            <li type="disc">Sleepy</li>
            <li type="disc">Happy</li>

       This is extremely useful for creating tables.  For example:

          print table({-border=>undef},
                  caption('When Should You Eat Your Vegetables?'),
                     th(['Vegetable', 'Breakfast','Lunch','Dinner']),
                     td(['Tomatoes' , 'no', 'yes', 'yes']),
                     td(['Broccoli' , 'no', 'no',  'yes']),
                     td(['Onions'   , 'yes','yes', 'yes'])


       Consider this bit of code:

          print blockquote(em('Hi'),'mom!'));

       It will ordinarily return the string that you probably expect, namely:

          <blockquote><em>Hi</em> mom!</blockquote>

       Note the space between the element "Hi" and the element "mom!". puts the extra space there using array
       interpolation, which is controlled by the magic $" variable.  Sometimes this extra space is not what you want,
       for example, when you are trying to align a series of images.  In this case, you can simply change the value of
       $" to an empty string.

             local($") = '';
             print blockquote(em('Hi'),'mom!'));

       I suggest you put the code in a block as shown here.  Otherwise the change to $" will affect all subsequent
       code until you explicitly reset it.


       A few HTML tags don't follow the standard pattern for various reasons.

       comment() generates an HTML comment (<!-- comment -->).  Call it like

           print comment('here is my comment');

       Because of conflicts with built-in Perl functions, the following functions begin with initial caps:


       In addition, start_html(), end_html(), start_form(), end_form(), start_multipart_form() and all the fill-out
       form tags are special.  See their respective sections.


       By default, all HTML that is emitted by the form-generating functions is passed through a function called

       $escaped_string = escapeHTML("unescaped string");
           Escape HTML formatting characters in a string.

       Provided that you have specified a character set of ISO-8859-1 (the default), the standard HTML escaping rules
       will be used.  The "<" character becomes "&lt;", ">" becomes "&gt;", "&" becomes "&amp;", and the quote charac-
       ter becomes "&quot;".  In addition, the hexadecimal 0x8b and 0x9b characters, which some browsers incorrectly
       interpret as the left and right angle-bracket characters, are replaced by their numeric character entities
       ("&#8249" and "&#8250;").  If you manually change the charset, either by calling the charset() method explic-
       itly or by passing a -charset argument to header(), then all characters will be replaced by their numeric enti-
       ties, since has no lookup table for all the possible encodings.

       The automatic escaping does not apply to other shortcuts, such as h1().  You should call escapeHTML() yourself
       on untrusted data in order to protect your pages against nasty tricks that people may enter into guestbooks,
       etc..  To change the character set, use charset().  To turn autoescaping off completely, use autoEscape(0):

       $charset = charset([$charset]);
           Get or set the current character set.

       $flag = autoEscape([$flag]);
           Get or set the value of the autoescape flag.


       By default, all the HTML produced by these functions comes out as one long line without carriage returns or
       indentation. This is yuck, but it does reduce the size of the documents by 10-20%.  To get pretty-printed out-
       put, please use CGI::Pretty, a subclass contributed by Brian Paulsen.

       General note  The various form-creating methods all return strings to the caller, containing the tag or tags
       that will create the requested form element.  You are responsible for actually printing out these strings.
       It's set up this way so that you can place formatting tags around the form elements.

       Another note The default values that you specify for the forms are only used the first time the script is
       invoked (when there is no query string).  On subsequent invocations of the script (when there is a query
       string), the former values are used even if they are blank.

       If you want to change the value of a field from its previous value, you have two choices:

       (1) call the param() method to set it.

       (2) use the -override (alias -force) parameter (a new feature in version 2.15).  This forces the default value
       to be used, regardless of the previous value:

          print textfield(-name=>'field_name',
                                  -default=>'starting value',

       Yet another note By default, the text and labels of form elements are escaped according to HTML rules.  This
       means that you can safely use "<CLICK ME>" as the label for a button.  However, it also interferes with your
       ability to incorporate special HTML character sequences, such as &Aacute;, into your fields.  If you wish to
       turn off automatic escaping, call the autoEscape() method with a false value immediately after creating the CGI

          $query = new CGI;

       A Lurking Trap! Some of the form-element generating methods return multiple tags.  In a scalar context, the
       tags will be concatenated together with spaces, or whatever is the current value of the $" global.  In a list
       context, the methods will return a list of elements, allowing you to modify them if you wish.  Usually you will
       not notice this behavior, but beware of this:


       end_form() produces several tags, and only the first of them will be printed because the format only expects
       one value.



          print isindex(-action=>$action);


          print isindex($action);

       Prints out an <isindex> tag.  Not very exciting.  The parameter -action specifies the URL of the script to pro-
       cess the query.  The default is to process the query with the current script.


           print start_form(-method=>$method,
             <... various form stuff ...>
           print endform;


           print start_form($method,$action,$encoding);
             <... various form stuff ...>
           print endform;

       start_form() will return a <form> tag with the optional method, action and form encoding that you specify.  The
       defaults are:

           method: POST
           action: this script
           enctype: application/x-www-form-urlencoded

       endform() returns the closing </form> tag.

       Start_form()'s enctype argument tells the browser how to package the various fields of the form before sending
       the form to the server.  Two values are possible:

       Note: This method was previously named startform(), and startform() is still recognized as an alias.

           This is the older type of encoding used by all browsers prior to Netscape 2.0.  It is compatible with many
           CGI scripts and is suitable for short fields containing text data.  For your convenience, stores the
           name of this encoding type in &CGI::URL_ENCODED.

           This is the newer type of encoding introduced by Netscape 2.0.  It is suitable for forms that contain very
           large fields or that are intended for transferring binary data.  Most importantly, it enables the "file
           upload" feature of Netscape 2.0 forms.  For your convenience, stores the name of this encoding type
           in &CGI::MULTIPART

           Forms that use this type of encoding are not easily interpreted by CGI scripts unless they use or
           another library designed to handle them.

           If XHTML is activated (the default), then forms will be automatically created using this type of encoding.

       For compatibility, the start_form() method uses the older form of encoding by default.  If you want to use the
       newer form of encoding by default, you can call start_multipart_form() instead of start_form().

       JAVASCRIPTING: The -name and -onSubmit parameters are provided for use with JavaScript.  The -name parameter
       gives the form a name so that it can be identified and manipulated by JavaScript functions.  -onSubmit should
       point to a JavaScript function that will be executed just before the form is submitted to your server.  You can
       use this opportunity to check the contents of the form for consistency and completeness.  If you find something
       wrong, you can put up an alert box or maybe fix things up yourself.  You can abort the submission by returning
       false from this function.

       Usually the bulk of JavaScript functions are defined in a <script> block in the HTML header and -onSubmit
       points to one of these function call.  See start_html() for details.


       After starting a form, you will typically create one or more textfields, popup menus, radio groups and other
       form elements.  Each of these elements takes a standard set of named arguments.  Some elements also have
       optional arguments.  The standard arguments are as follows:

           The name of the field. After submission this name can be used to retrieve the field's value using the
           param() method.

       -value, -values
           The initial value of the field which will be returned to the script after form submission.  Some form ele-
           ments, such as text fields, take a single scalar -value argument. Others, such as popup menus, take a ref-
           erence to an array of values. The two arguments are synonyms.

           A numeric value that sets the order in which the form element receives focus when the user presses the tab
           key. Elements with lower values receive focus first.

       -id A string identifier that can be used to identify this element to JavaScript and DHTML.

           A boolean, which, if true, forces the element to take on the value specified by -value, overriding the
           sticky behavior described earlier for the -no_sticky pragma.

       -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut, -onSelect
           These are used to assign JavaScript event handlers. See the JavaScripting section for more details.

       Other common arguments are described in the next section. In addition to these, all attributes described in the
       HTML specifications are supported.


           print textfield(-name=>'field_name',
                           -value=>'starting value',

           print textfield('field_name','starting value',50,80);

       textfield() will return a text input field.

       1.  The first parameter is the required name for the field (-name).

       2.  The optional second parameter is the default starting value for the field contents (-value, formerly known
           as -default).

       3.  The optional third parameter is the size of the field in
                 characters (-size).

       4.  The optional fourth parameter is the maximum number of characters the
                 field will accept (-maxlength).

       As with all these methods, the field will be initialized with its previous contents from earlier invocations of
       the script.  When the form is processed, the value of the text field can be retrieved with:

              $value = param('foo');

       If you want to reset it from its initial value after the script has been called once, you can do so like this:

              param('foo',"I'm taking over this value!");


          print textarea(-name=>'foo',
                                 -default=>'starting value',


          print textarea('foo','starting value',10,50);

       textarea() is just like textfield, but it allows you to specify rows and columns for a multiline text entry
       box.  You can provide a starting value for the field, which can be long and contain multiple lines.


          print password_field(-name=>'secret',
                                       -value=>'starting value',

          print password_field('secret','starting value',50,80);

       password_field() is identical to textfield(), except that its contents will be starred out on the web page.


           print filefield(-name=>'uploaded_file',
                                   -default=>'starting value',

           print filefield('uploaded_file','starting value',50,80);

       filefield() will return a file upload field for Netscape 2.0 browsers.  In order to take full advantage of this
       you must use the new multipart encoding scheme for the form.  You can do this either by calling start_form()
       with an encoding type of &CGI::MULTIPART, or by calling the new method start_multipart_form() instead of
       vanilla start_form().

       1.  The first parameter is the required name for the field (-name).

       2.  The optional second parameter is the starting value for the field contents to be used as the default file
           name (-default).

           For security reasons, browsers don't pay any attention to this field, and so the starting value will always
           be blank.  Worse, the field loses its "sticky" behavior and forgets its previous contents.  The starting
           value field is called for in the HTML specification, however, and possibly some browser will eventually
           provide support for it.

       3.  The optional third parameter is the size of the field in characters (-size).

       4.  The optional fourth parameter is the maximum number of characters the field will accept (-maxlength).

       When the form is processed, you can retrieve the entered filename by calling param():

              $filename = param('uploaded_file');

       Different browsers will return slightly different things for the name.  Some browsers return the filename only.
       Others return the full path to the file, using the path conventions of the user's machine.  Regardless, the
       name returned is always the name of the file on the user's machine, and is unrelated to the name of the tempo-
       rary file that creates during upload spooling (see below).

       The filename returned is also a file handle.  You can read the contents of the file using standard Perl file
       reading calls:

               # Read a text file and print it out
               while (<$filename>) {

               # Copy a binary file to somewhere safe
               open (OUTFILE,">>/usr/local/web/users/feedback");
               while ($bytesread=read($filename,$buffer,1024)) {
                  print OUTFILE $buffer;

       However, there are problems with the dual nature of the upload fields.  If you "use strict", then Perl will
       complain when you try to use a string as a filehandle.  You can get around this by placing the file reading
       code in a block containing the "no strict" pragma.  More seriously, it is possible for the remote user to type
       garbage into the upload field, in which case what you get from param() is not a filehandle at all, but a

       To be safe, use the upload() function (new in version 2.47).  When called with the name of an upload field,
       upload() returns a filehandle, or undef if the parameter is not a valid filehandle.

            $fh = upload('uploaded_file');
            while (<$fh>) {

       In an list context, upload() will return an array of filehandles.  This makes it possible to create forms that
       use the same name for multiple upload fields.

       This is the recommended idiom.

       When a file is uploaded the browser usually sends along some information along with it in the format of head-
       ers.  The information usually includes the MIME content type.  Future browsers may send other information as
       well (such as modification date and size). To retrieve this information, call uploadInfo().  It returns a ref-
       erence to an associative array containing all the document headers.

              $filename = param('uploaded_file');
              $type = uploadInfo($filename)->{'Content-Type'};
              unless ($type eq 'text/html') {
                 die "HTML FILES ONLY!";

       If you are using a machine that recognizes "text" and "binary" data modes, be sure to understand when and how
       to use them (see the Camel book).  Otherwise you may find that binary files are corrupted during file uploads.

       There are occasionally problems involving parsing the uploaded file.  This usually happens when the user
       presses "Stop" before the upload is finished.  In this case, will return undef for the name of the
       uploaded file and set cgi_error() to the string "400 Bad request (malformed multipart POST)".  This error mes-
       sage is designed so that you can incorporate it into a status code to be sent to the browser.  Example:

          $file = upload('uploaded_file');
          if (!$file && cgi_error) {
             print header(-status=>cgi_error);
             exit 0;

       You are free to create a custom HTML page to complain about the error, if you wish.

       You can set up a callback that will be called whenever a file upload is being read during the form processing.
       This is much like the UPLOAD_HOOK facility available in Apache::Request, with the exception that the first
       argument to the callback is an Apache::Upload object, here it's the remote filename.

        $q = CGI->new(\&hook,$data);

        sub hook
               my ($filename, $buffer, $bytes_read, $data) = @_;
               print  "Read $bytes_read bytes of $filename\n";

       If using the function-oriented interface, call the CGI::upload_hook() method before calling param() or any
       other CGI functions:


       This method is not exported by default.  You will have to import it explicitly if you wish to use it without
       the CGI:: prefix.

       If you are using on a Windows platform and find that binary files get slightly larger when uploaded but
       that text files remain the same, then you have forgotten to activate binary mode on the output filehandle.  Be
       sure to call binmode() on any handle that you create to write the uploaded file to disk.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut and -onSelect parameters are recog-
       nized.  See textfield() for details.


          print popup_menu('menu_name',


          %labels = ('eenie'=>'your first choice',
                     'meenie'=>'your second choice',
                     'minie'=>'your third choice');
          %attributes = ('eenie'=>{'class'=>'class of first choice'});
          print popup_menu('menu_name',

               -or (named parameter style)-

          print popup_menu(-name=>'menu_name',

       popup_menu() creates a menu.

       1.  The required first argument is the menu's name (-name).

       2.  The required second argument (-values) is an array reference containing the list of menu items in the menu.
           You can pass the method an anonymous array, as shown in the example, or a reference to a named array, such
           as "\@foo".

       3.  The optional third parameter (-default) is the name of the default menu choice.  If not specified, the
           first item will be the default.  The values of the previous choice will be maintained across queries.

       4.  The optional fourth parameter (-labels) is provided for people who want to use different values for the
           user-visible label inside the popup menu and the value returned to your script.  It's a pointer to an asso-
           ciative array relating menu values to user-visible labels.  If you leave this parameter blank, the menu
           values will be displayed by default.  (You can also leave a label undefined if you want to).

       5.  The optional fifth parameter (-attributes) is provided to assign any of the common HTML attributes to an
           individual menu item. It's a pointer to an associative array relating menu values to another associative
           array with the attribute's name as the key and the attribute's value as the value.

       When the form is processed, the selected value of the popup menu can be retrieved using:

             $popup_menu_value = param('menu_name');


       Named parameter style

         print popup_menu(-name=>'menu_name',
                         -values=>[qw/eenie meenie minie/,
                                                    -values => ['moe','catch'],

         Old style
         print popup_menu('menu_name',
                          optgroup('optgroup_name', ['moe', 'catch'],

       optgroup() creates an option group within a popup menu.

       1.  The required first argument (-name) is the label attribute of the optgroup and is not inserted in the
           parameter list of the query.

       2.  The required second argument (-values)  is an array reference containing the list of menu items in the
           menu.  You can pass the method an anonymous array, as shown in the example, or a reference to a named
           array, such as \@foo.  If you pass a HASH reference, the keys will be used for the menu values, and the
           values will be used for the menu labels (see -labels below).

       3.  The optional third parameter (-labels) allows you to pass a reference to an associative array containing
           user-visible labels for one or more of the menu items.  You can use this when you want the user to see one
           menu string, but have the browser return your program a different one.  If you don't specify this, the
           value string will be used instead ("eenie", "meenie" and "minie" in this example).  This is equivalent to
           using a hash reference for the -values parameter.

       4.  An optional fourth parameter (-labeled) can be set to a true value and indicates that the values should be
           used as the label attribute for each option element within the optgroup.

       5.  An optional fifth parameter (-novals) can be set to a true value and indicates to suppress the val attribut
           in each option element within the optgroup.

           See the discussion on optgroup at W3C (
           for details.

       6.  An optional sixth parameter (-attributes) is provided to assign any of the common HTML attributes to an
           individual menu item. It's a pointer to an associative array relating menu values to another associative
           array with the attribute's name as the key and the attribute's value as the value.


          print scrolling_list('list_name',

          print scrolling_list('list_name',


          print scrolling_list(-name=>'list_name',

       scrolling_list() creates a scrolling list.

       1.  The first and second arguments are the list name (-name) and values (-values).  As in the popup menu, the
           second argument should be an array reference.

       2.  The optional third argument (-default) can be either a reference to a list containing the values to be
           selected by default, or can be a single value to select.  If this argument is missing or undefined, then
           nothing is selected when the list first appears.  In the named parameter version, you can use the synonym
           "-defaults" for this parameter.

       3.  The optional fourth argument is the size of the list (-size).

       4.  The optional fifth argument can be set to true to allow multiple simultaneous selections (-multiple).  Oth-
           erwise only one selection will be allowed at a time.

       5.  The optional sixth argument is a pointer to an associative array containing long user-visible labels for
           the list items (-labels).  If not provided, the values will be displayed.

       6.  The optional sixth parameter (-attributes) is provided to assign any of the common HTML attributes to an
           individual menu item. It's a pointer to an associative array relating menu values to another associative
           array with the attribute's name as the key and the attribute's value as the value.

           When this form is processed, all selected list items will be returned as a list under the parameter name
           'list_name'.  The values of the selected items can be retrieved with:

                 @selected = param('list_name');


          print checkbox_group(-name=>'group_name',

          print checkbox_group('group_name',


          print checkbox_group(-name=>'group_name',

       checkbox_group() creates a list of checkboxes that are related by the same name.

       1.  The first and second arguments are the checkbox name and values, respectively (-name and -values).  As in
           the popup menu, the second argument should be an array reference.  These values are used for the user-read-
           able labels printed next to the checkboxes as well as for the values passed to your script in the query

       2.  The optional third argument (-default) can be either a reference to a list containing the values to be
           checked by default, or can be a single value to checked.  If this argument is missing or undefined, then
           nothing is selected when the list first appears.

       3.  The optional fourth argument (-linebreak) can be set to true to place line breaks between the checkboxes so
           that they appear as a vertical list.  Otherwise, they will be strung together on a horizontal line.

       The optional b<-labels> argument is a pointer to an associative array relating the checkbox values to the user-
       visible labels that will be printed next to them.  If not provided, the values will be used as the default.

       Modern browsers can take advantage of the optional parameters -rows, and -columns.  These parameters cause
       checkbox_group() to return an HTML3 compatible table containing the checkbox group formatted with the specified
       number of rows and columns.  You can provide just the -columns parameter if you wish; checkbox_group will cal-
       culate the correct number of rows for you.

       The optional -attributes argument is provided to assign any of the common HTML attributes to an individual menu
       item. It's a pointer to an associative array relating menu values to another associative array with the
       attribute's name as the key and the attribute's value as the value.

       The optional -tabindex argument can be used to control the order in which radio buttons receive focus when the
       user presses the tab button.  If passed a scalar numeric value, the first element in the group will receive
       this tab index and subsequent elements will be incremented by one.  If given a reference to an array of radio
       button values, then the indexes will be jiggered so that the order specified in the array will correspond to
       the tab order.  You can also pass a reference to a hash in which the hash keys are the radio button values and
       the values are the tab indexes of each button.  Examples:

         -tabindex => 100    #  this group starts at index 100 and counts up
         -tabindex => ['moe','minie','eenie','meenie']  # tab in this order
         -tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order

       When the form is processed, all checked boxes will be returned as a list under the parameter name 'group_name'.
       The values of the "on" checkboxes can be retrieved with:

             @turned_on = param('group_name');

       The value returned by checkbox_group() is actually an array of button elements.  You can capture them and use
       them within tables, lists, or in other creative ways:

           @h = checkbox_group(-name=>'group_name',-values=>\@values);


           print checkbox(-name=>'checkbox_name',
                                  -label=>'CLICK ME');


           print checkbox('checkbox_name','checked','ON','CLICK ME');

       checkbox() is used to create an isolated checkbox that isn't logically related to any others.

       1.  The first parameter is the required name for the checkbox (-name).  It will also be used for the user-read-
           able label printed next to the checkbox.

       2.  The optional second parameter (-checked) specifies that the checkbox is turned on by default.  Synonyms are
           -selected and -on.

       3.  The optional third parameter (-value) specifies the value of the checkbox when it is checked.  If not pro-
           vided, the word "on" is assumed.

       4.  The optional fourth parameter (-label) is the user-readable label to be attached to the checkbox.  If not
           provided, the checkbox name is used.

       The value of the checkbox can be retrieved using:

           $turned_on = param('checkbox_name');


          print radio_group(-name=>'group_name',


          print radio_group('group_name',['eenie','meenie','minie'],


          print radio_group(-name=>'group_name',

       radio_group() creates a set of logically-related radio buttons (turning one member of the group on turns the
       others off)

       1.  The first argument is the name of the group and is required (-name).

       2.  The second argument (-values) is the list of values for the radio buttons.  The values and the labels that
           appear on the page are identical.  Pass an array reference in the second argument, either using an anony-
           mous array, as shown, or by referencing a named array as in "\@foo".

       3.  The optional third parameter (-default) is the name of the default button to turn on. If not specified, the
           first item will be the default.  You can provide a nonexistent button name, such as "-" to start up with no
           buttons selected.

       4.  The optional fourth parameter (-linebreak) can be set to 'true' to put line breaks between the buttons,
           creating a vertical list.

       5.  The optional fifth parameter (-labels) is a pointer to an associative array relating the radio button val-
           ues to user-visible labels to be used in the display.  If not provided, the values themselves are dis-

       All modern browsers can take advantage of the optional parameters -rows, and -columns.  These parameters cause
       radio_group() to return an HTML3 compatible table containing the radio group formatted with the specified num-
       ber of rows and columns.  You can provide just the -columns parameter if you wish; radio_group will calculate
       the correct number of rows for you.

       To include row and column headings in the returned table, you can use the -rowheader and -colheader parameters.
       Both of these accept a pointer to an array of headings to use.  The headings are just decorative.  They don't
       reorganize the interpretation of the radio buttons -- they're still a single named unit.

       The optional -tabindex argument can be used to control the order in which radio buttons receive focus when the
       user presses the tab button.  If passed a scalar numeric value, the first element in the group will receive
       this tab index and subsequent elements will be incremented by one.  If given a reference to an array of radio
       button values, then the indexes will be jiggered so that the order specified in the array will correspond to
       the tab order.  You can also pass a reference to a hash in which the hash keys are the radio button values and
       the values are the tab indexes of each button.  Examples:

         -tabindex => 100    #  this group starts at index 100 and counts up
         -tabindex => ['moe','minie','eenie','meenie']  # tab in this order
         -tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order

       The optional -attributes argument is provided to assign any of the common HTML attributes to an individual menu
       item. It's a pointer to an associative array relating menu values to another associative array with the
       attribute's name as the key and the attribute's value as the value.

       When the form is processed, the selected radio button can be retrieved using:

             $which_radio_button = param('group_name');

       The value returned by radio_group() is actually an array of button elements.  You can capture them and use them
       within tables, lists, or in other creative ways:

           @h = radio_group(-name=>'group_name',-values=>\@values);


          print submit(-name=>'button_name',


          print submit('button_name','value');

       submit() will create the query submission button.  Every form should have one of these.

       1.  The first argument (-name) is optional.  You can give the button a name if you have several submission but-
           tons in your form and you want to distinguish between them.

       2.  The second argument (-value) is also optional.  This gives the button a value that will be passed to your
           script in the query string. The name will also be used as the user-visible label.

       3.  You can use -label as an alias for -value.  I always get confused about which of -name and -value changes
           the user-visible label on the button.

       You can figure out which button was pressed by using different values for each one:

            $which_one = param('button_name');


          print reset

       reset() creates the "reset" button.  Note that it restores the form to its value from the last time the script
       was called, NOT necessarily to the defaults.

       Note that this conflicts with the Perl reset() built-in.  Use CORE::reset() to get the original reset function.


          print defaults('button_label')

       defaults() creates a button that, when invoked, will cause the form to be completely reset to its defaults,
       wiping out all the changes the user ever made.


               print hidden(-name=>'hidden_name',


               print hidden('hidden_name','value1','value2'...);

       hidden() produces a text field that can't be seen by the user.  It is useful for passing state variable infor-
       mation from one invocation of the script to the next.

       1.  The first argument is required and specifies the name of this field (-name).

       2.  The second argument is also required and specifies its value (-default).  In the named parameter style of
           calling, you can provide a single value here or a reference to a whole list

       Fetch the value of a hidden field this way:

            $hidden_value = param('hidden_name');

       Note, that just like all the other form elements, the value of a hidden field is "sticky".  If you want to
       replace a hidden field with some other values after the script has been called once you'll have to do it manu-



            print image_button(-name=>'button_name',


            print image_button('button_name','/source/URL','MIDDLE');

       image_button() produces a clickable image.  When it's clicked on the position of the click is returned to your
       script as "button_name.x" and "button_name.y", where "button_name" is the name you've assigned to it.

       1.  The first argument (-name) is required and specifies the name of this field.

       2.  The second argument (-src) is also required and specifies the URL

       3. The third option (-align, optional) is an alignment type, and may be TOP, BOTTOM or MIDDLE

       Fetch the value of the button this way:
            $x = param('button_name.x');
            $y = param('button_name.y');


            print button(-name=>'button_name',
                                 -value=>'user visible label',


            print button('button_name',"do_something()");

       button() produces a button that is compatible with Netscape 2.0's JavaScript.  When it's pressed the fragment
       of JavaScript code pointed to by the -onClick parameter will be executed.  On non-Netscape browsers this form
       element will probably not even display.

       Netscape browsers versions 1.1 and higher, and all versions of Internet Explorer, support a so-called "cookie"
       designed to help maintain state within a browser session. has several methods that support cookies.

       A cookie is a name=value pair much like the named parameters in a CGI query string.  CGI scripts create one or
       more cookies and send them to the browser in the HTTP header.  The browser maintains a list of cookies that
       belong to a particular Web server, and returns them to the CGI script during subsequent interactions.

       In addition to the required name=value pair, each cookie has several optional attributes:

       1. an expiration time
           This is a time/date string (in a special GMT format) that indicates when a cookie expires.  The cookie will
           be saved and returned to your script until this expiration date is reached if the user exits the browser
           and restarts it.  If an expiration date isn't specified, the cookie will remain active until the user quits
           the browser.

       2. a domain
           This is a partial or complete domain name for which the cookie is valid.  The browser will return the
           cookie to any host that matches the partial domain name.  For example, if you specify a domain name of
           "", then the browser will return the cookie to Web servers running on any of the machines
           "", "", "", etc.  Domain names must contain at
           least two periods to prevent attempts to match on top level domains like ".edu".  If no domain is speci-
           fied, then the browser will only return the cookie to servers on the host the cookie originated from.

       3. a path
           If you provide a cookie path attribute, the browser will check it against your script's URL before return-
           ing the cookie.  For example, if you specify the path "/cgi-bin", then the cookie will be returned to each
           of the scripts "/cgi-bin/", "/cgi-bin/", and "/cgi-bin/customer_service/", but
           not to the script "/cgi-private/".  By default, path is set to "/", which causes the cookie to
           be sent to any CGI script on your site.

       4. a "secure" flag
           If the "secure" attribute is set, the cookie will only be sent to your script if the CGI request is occur-
           ring on a secure channel, such as SSL.

       The interface to HTTP cookies is the cookie() method:

           $cookie = cookie(-name=>'sessionID',
           print header(-cookie=>$cookie);

       cookie() creates a new cookie.  Its parameters include:

           The name of the cookie (required).  This can be any string at all.  Although browsers limit their cookie
           names to non-whitespace alphanumeric characters, removes this restriction by escaping and unescaping
           cookies behind the scenes.

           The value of the cookie.  This can be any scalar value, array reference, or even associative array refer-
           ence.  For example, you can store an entire associative array into a cookie this way:

                   $cookie=cookie(-name=>'family information',

           The optional partial path for which this cookie will be valid, as described above.

           The optional partial domain for which this cookie will be valid, as described above.

           The optional expiration date for this cookie.  The format is as described in the section on the header()

                   "+1h"  one hour from now

           If set to true, this cookie will only be used within a secure SSL session.

       The cookie created by cookie() must be incorporated into the HTTP header within the string returned by the
       header() method:

               print header(-cookie=>$my_cookie);

       To create multiple cookies, give header() an array reference:

               $cookie1 = cookie(-name=>'riddle_name',
                                         -value=>"The Sphynx's Question");
               $cookie2 = cookie(-name=>'answers',
               print header(-cookie=>[$cookie1,$cookie2]);

       To retrieve a cookie, request it by name by calling cookie() method without the -value parameter:

               use CGI;
               $query = new CGI;
               $riddle = cookie('riddle_name');
               %answers = cookie('answers');

       Cookies created with a single scalar value, such as the "riddle_name" cookie, will be returned in that form.
       Cookies with array and hash values can also be retrieved.

       The cookie and CGI namespaces are separate.  If you have a parameter named 'answers' and a cookie named
       'answers', the values retrieved by param() and cookie() are independent of each other.  However, it's simple to
       turn a CGI parameter into a cookie, and vice-versa:

          # turn a CGI parameter into a cookie
          # vice-versa

       See the cookie.cgi example script for some ideas on how to use cookies effectively.

       It's possible for scripts to write into several browser panels and windows using the HTML 4 frame mecha-
       nism.  There are three techniques for defining new frames programmatically:

       1. Create a <Frameset> document
           After writing out the HTTP header, instead of creating a standard HTML document using the start_html()
           call, create a <frameset> document that defines the frames on the page.  Specify your script(s) (with
           appropriate parameters) as the SRC for each of the frames.

           There is no specific support for creating <frameset> sections in, but the HTML is very simple to
           write.  See the frame documentation in Netscape's home pages for details


       2. Specify the destination for the document in the HTTP header
           You may provide a -target parameter to the header() method:

               print header(-target=>'ResultsWindow');

           This will tell the browser to load the output of your script into the frame named "ResultsWindow".  If a
           frame of that name doesn't already exist, the browser will pop up a new window and load your script's docu-
           ment into that.  There are a number of magic names that you can use for targets.  See the frame documents
           on Netscape's home pages for details.

       3. Specify the destination for the document in the <form> tag
           You can specify the frame to load in the FORM tag itself.  With it looks like this:

               print start_form(-target=>'ResultsWindow');

           When your script is reinvoked by the form, its output will be loaded into the frame named "ResultsWindow".
           If one doesn't already exist a new window will be created.

       The script "frameset.cgi" in the examples directory shows one way to create pages in which the fill-out form
       and the response live in side-by-side frames.

       Netscape versions 2.0 and higher incorporate an interpreted language called JavaScript. Internet Explorer, 3.0
       and higher, supports a closely-related dialect called JScript. JavaScript isn't the same as Java, and certainly
       isn't at all the same as Perl, which is a great pity. JavaScript allows you to programatically change the con-
       tents of fill-out forms, create new windows, and pop up dialog box from within Netscape itself. From the point
       of view of CGI scripting, JavaScript is quite useful for validating fill-out forms prior to submitting them.

       You'll need to know JavaScript in order to use it. There are many good sources in bookstores and on the web.

       The usual way to use JavaScript is to define a set of functions in a <SCRIPT> block inside the HTML header and
       then to register event handlers in the various elements of the page. Events include such things as the mouse
       passing over a form element, a button being clicked, the contents of a text field changing, or a form being
       submitted. When an event occurs that involves an element that has registered an event handler, its associated
       JavaScript code gets called.

       The elements that can register event handlers include the <BODY> of an HTML document, hypertext links, all the
       various elements of a fill-out form, and the form itself. There are a large number of events, and each applies
       only to the elements for which it is relevant. Here is a partial list:

           The browser is loading the current document. Valid in:

                + The HTML <BODY> section only.

           The browser is closing the current page or frame. Valid for:

                + The HTML <BODY> section only.

           The user has pressed the submit button of a form. This event happens just before the form is submitted, and
           your function can return a value of false in order to abort the submission.  Valid for:

                + Forms only.

           The mouse has clicked on an item in a fill-out form. Valid for:

                + Buttons (including submit, reset, and image buttons)
                + Checkboxes
                + Radio buttons

           The user has changed the contents of a field. Valid for:

                + Text fields
                + Text areas
                + Password fields
                + File fields
                + Popup Menus
                + Scrolling lists

           The user has selected a field to work with. Valid for:

                + Text fields
                + Text areas
                + Password fields
                + File fields
                + Popup Menus
                + Scrolling lists

           The user has deselected a field (gone to work somewhere else).  Valid for:

                + Text fields
                + Text areas
                + Password fields
                + File fields
                + Popup Menus
                + Scrolling lists

           The user has changed the part of a text field that is selected.  Valid for:

                + Text fields
                + Text areas
                + Password fields
                + File fields

           The mouse has moved over an element.

                + Text fields
                + Text areas
                + Password fields
                + File fields
                + Popup Menus
                + Scrolling lists

           The mouse has moved off an element.

                + Text fields
                + Text areas
                + Password fields
                + File fields
                + Popup Menus
                + Scrolling lists

       In order to register a JavaScript event handler with an HTML element, just use the event name as a parameter
       when you call the corresponding CGI method. For example, to have your validateAge() JavaScript code executed
       every time the textfield named "age" changes, generate the field like this:

        print textfield(-name=>'age',-onChange=>"validateAge(this)");

       This example assumes that you've already declared the validateAge() function by incorporating it into a
       <SCRIPT> block. The start_html() method provides a convenient way to create this section.

       Similarly, you can create a form that checks itself over for consistency and alerts the user if some essential
       value is missing by creating it this way:
         print startform(-onSubmit=>"validateMe(this)");

       See the javascript.cgi script for a demonstration of how this all works.

LIMITED SUPPORT FOR CASCADING STYLE SHEETS has limited support for HTML3's cascading style sheets (css).  To incorporate a stylesheet into your
       document, pass the start_html() method a -style parameter.  The value of this parameter may be a scalar, in
       which case it is treated as the source URL for the stylesheet, or it may be a hash reference.  In the latter
       case you should provide the hash with one or more of -src or -code.  -src points to a URL where an externally-
       defined stylesheet can be found.  -code points to a scalar value to be incorporated into a <style> section.
       Style definitions in -code override similarly-named ones in -src, hence the name "cascading."

       You may also specify the type of the stylesheet by adding the optional -type parameter to the hash pointed to
       by -style.  If not specified, the style defaults to 'text/css'.

       To refer to a style within the body of your document, add the -class parameter to any HTML element:

           print h1({-class=>'Fancy'},'Welcome to the Party');

       Or define styles on the fly with the -style parameter:

           print h1({-style=>'Color: red;'},'Welcome to Hell');

       You may also use the new span() element to apply a style to a section of text:

           print span({-style=>'Color: red;'},
                      h1('Welcome to Hell'),
                      "Where did that handbasket get to?"

       Note that you must import the ":html3" definitions to have the span() method available.  Here's a quick and
       dirty example of using CSS's.  See the CSS specification at for more

           use CGI qw/:standard :html3/;

           #here's a stylesheet incorporated directly into the page
           P.Tip {
               margin-right: 50pt;
               margin-left: 50pt;
               color: red;
           P.Alert {
               font-size: 30pt;
               font-family: sans-serif;
             color: red;
           print header();
           print start_html( -title=>'CGI with Style',
           print h1('CGI with Style'),
                   "Better read the cascading style sheet spec before playing with this!"),
                 span({-style=>'color: magenta'},
                      "Look Mom, no hands!",
                      "Whooo wee!"
           print end_html;

       Pass an array reference to -code or -src in order to incorporate multiple stylesheets into your document.

       Should you wish to incorporate a verbatim stylesheet that includes arbitrary formatting in the header, you may
       pass a -verbatim tag to the -style hash, as follows:

       print start_html (-STYLE  =>  {-verbatim => '@import url("/server-common/css/'.$cssFile.'");',
                             -src      =>  '/server-common/css/core.css'}); </blockquote></pre>

       This will generate an HTML header that contains this:

        <link rel="stylesheet" type="text/css"  href="/server-common/css/core.css">
          <style type="text/css">
          @import url("/server-common/css/main.css");

       Any additional arguments passed in the -style value will be incorporated into the <link> tag.  For example:

                                 -media => 'all'});

       This will give:

        <link rel="stylesheet" type="text/css" href="/styles/print.css" media="all"/>
        <link rel="stylesheet" type="text/css" href="/styles/layout.css" media="all"/>


       To make more complicated <link> tags, use the Link() function and pass it to start_html() in the -head argu-
       ment, as in:

         @h = (Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/ss.css',-media=>'all'}),
         print start_html({-head=>\@h})

       If you are running the script from the command line or in the perl debugger, you can pass the script a list of
       keywords or parameter=value pairs on the command line or from standard input (you don't have to worry about
       tricking your script into reading from environment variables).  You can pass keywords like this:

  keyword1 keyword2 keyword3

       or this:


       or this:

  name1=value1 name2=value2

       or this:


       To turn off this feature, use the -no_debug pragma.

       To test the POST method, you may enable full debugging with the -debug pragma.  This will allow you to feed
       newline-delimited name=value pairs to the script on standard input.

       When debugging, you can use quotes and backslashes to escape characters in the familiar shell manner, letting
       you place spaces and other funny characters in your parameter=value pairs:

 "name1='I am a long value'" "name2=two\ words"

       Finally, you can set the path info for the script by prefixing the first name/value parameter with the path
       followed by a question mark (?):



       The Dump() method produces a string consisting of all the query's name/value pairs formatted nicely as a nested
       list.  This is useful for debugging purposes:

           print Dump

       Produces something that looks like:


       As a shortcut, you can interpolate the entire CGI object into a string and it will be replaced with the a nice
       HTML dump shown above:

           $query=new CGI;
           print "<h2>Current Values</h2> $query\n";

       Some of the more useful environment variables can be fetched through this interface.  The methods are as fol-

           Return a list of MIME types that the remote browser accepts. If you give this method a single argument cor-
           responding to a MIME type, as in Accept('text/html'), it will return a floating point value corresponding
           to the browser's preference for this type from 0.0 (don't want) to 1.0.  Glob types (e.g. text/*) in the
           browser's accept list are handled correctly.

           Note that the capitalization changed between version 2.43 and 2.44 in order to avoid conflict with Perl's
           accept() function.

           Returns the HTTP_COOKIE variable, an HTTP extension implemented by Netscape browsers version 1.1 and
           higher, and all versions of Internet Explorer.  Cookies have a special format, and this method call just
           returns the raw form (?cookie dough).  See cookie() for ways of setting and retrieving cooked cookies.

           Called with no parameters, raw_cookie() returns the packed cookie structure.  You can separate it into
           individual cookies by splitting on the character sequence "; ".  Called with the name of a cookie,
           retrieves the unescaped form of the cookie.  You can use the regular cookie() method to get the names, or
           use the raw_fetch() method from the CGI::Cookie module.

           Returns the HTTP_USER_AGENT variable.  If you give this method a single argument, it will attempt to pat-
           tern match on it, allowing you to do something like user_agent(netscape);

           Returns additional path information from the script URL.  E.G. fetching /cgi-bin/your_script/addi-
           tional/stuff will result in path_info() returning "/additional/stuff".

           NOTE: The Microsoft Internet Information Server is broken with respect to additional path information.  If
           you use the Perl DLL library, the IIS server will attempt to execute the additional path information as a
           Perl script.  If you use the ordinary file associations mapping, the path information will be present in
           the environment, but incorrect.  The best thing to do is to avoid using additional path information in CGI
           scripts destined for use with IIS.

           As per path_info() but returns the additional path information translated into a physical path, e.g.

           The Microsoft IIS is broken with respect to the translated path as well.

           Returns either the remote host name or IP address.  if the former is unavailable.

       script_name() Return the script name as a partial URL, for self-refering scripts.
           Return the URL of the page the browser was viewing prior to fetching your script.  Not available for all

       auth_type ()
           Return the authorization/verification method in use for this script, if any.

       server_name ()
           Returns the name of the server, usually the machine's host name.

       virtual_host ()
           When using virtual hosts, returns the name of the host that the browser attempted to contact

       server_port ()
           Return the port that the server is listening on.

       virtual_port ()
           Like server_port() except that it takes virtual hosts into account.  Use this when running with virtual

       server_software ()
           Returns the server software and version number.

       remote_user ()
           Return the authorization/verification name used for user verification, if this script is protected.

       user_name ()
           Attempt to obtain the remote user's name, using a variety of different techniques.  This only works with
           older browsers such as Mosaic.  Newer browsers do not report the user name for privacy reasons!

           Returns the method used to access your script, usually one of 'POST', 'GET' or 'HEAD'.

           Returns the content_type of data submitted in a POST, generally multipart/form-data or applica-

           Called with no arguments returns the list of HTTP environment variables, including such things as
           HTTP_USER_AGENT, HTTP_ACCEPT_LANGUAGE, and HTTP_ACCEPT_CHARSET, corresponding to the like-named HTTP header
           fields in the request.  Called with the name of an HTTP header field, returns its value.  Capitalization
           and the use of hyphens versus underscores are not significant.

           For example, all three of these examples are equivalent:

              $requested_language = http('Accept-language');
              $requested_language = http('Accept_language');
              $requested_language = http('HTTP_ACCEPT_LANGUAGE');

           The same as http(), but operates on the HTTPS environment variables present when the SSL protocol is in
           effect.  Can be used to determine whether SSL is turned on.

       NPH, or "no-parsed-header", scripts bypass the server completely by sending the complete HTTP header directly
       to the browser.  This has slight performance benefits, but is of most use for taking advantage of HTTP exten-
       sions that are not directly supported by your server, such as server push and PICS headers.

       Servers use a variety of conventions for designating CGI scripts as NPH.  Many Unix servers look at the begin-
       ning of the script's name for the prefix "nph-".  The Macintosh WebSTAR server and Microsoft's Internet Infor-
       mation Server, in contrast, try to decide whether a program is an NPH script by examining the first line of
       script output. supports NPH scripts with a special NPH mode.  When in this mode, will output the necessary extra
       header information when the header() and redirect() methods are called.

       The Microsoft Internet Information Server requires NPH mode.  As of version 2.30, will automatically
       detect when the script is running under IIS and put itself into this mode.  You do not need to do this manu-
       ally, although it won't hurt anything if you do.  However, note that if you have applied Service Pack 6, much
       of the functionality of NPH scripts, including the ability to redirect while setting a cookie, b<do not work at
       all> on IIS without a special patch from Microsoft.  See
       cles/Q280/3/41.ASP: Non-Parsed Headers Stripped From CGI Applications That Have nph- Prefix in Name.

       In the use statement
           Simply add the "-nph" pragmato the list of symbols to be imported into your script:

                 use CGI qw(:standard -nph)

       By calling the nph() method:
           Call nph() with a non-zero parameter at any point after using in your program.


       By using -nph parameters
           in the header() and redirect()  statements:

                 print header(-nph=>1);

Server Push provides four simple functions for producing multipart documents of the type needed to implement server
       push.  These functions were graciously provided by Ed Jordan <>.  To import these into your
       namespace, you must import the ":push" set.  You are also advised to put the script into NPH mode and to set $|
       to 1 to avoid buffering problems.

       Here is a simple script that demonstrates server push:

         use CGI qw/:push -nph/;
         $| = 1;
         print multipart_init(-boundary=>'----here we go!');
         foreach (0 .. 4) {
             print multipart_start(-type=>'text/plain'),
                   "The current time is ",scalar(localtime),"\n";
             if ($_ < 4) {
                     print multipart_end;
             } else {
                     print multipart_final;
             sleep 1;

       This script initializes server push by calling multipart_init().  It then enters a loop in which it begins a
       new multipart section by calling multipart_start(), prints the current local time, and ends a multipart section
       with multipart_end().  It then sleeps a second, and begins again. On the final iteration, it ends the multipart
       section with multipart_final() rather than with multipart_end().


           Initialize the multipart system.  The -boundary argument specifies what MIME boundary string to use to sep-
           arate parts of the document.  If not provided, chooses a reasonable boundary for you.


           Start a new part of the multipart document using the specified MIME type.  If not specified, text/html is


           End a part.  You must remember to call multipart_end() once for each multipart_start(), except at the end
           of the last part of the multipart document when multipart_final() should be called instead of multi-


           End all parts.  You should call multipart_final() rather than multipart_end() at the end of the last part
           of the multipart document.

       Users interested in server push applications should also have a look at the CGI::Push module.

       Only Netscape Navigator supports server push.  Internet Explorer browsers do not.

Avoiding Denial of Service Attacks
       A potential problem with is that, by default, it attempts to process form POSTings no matter how large
       they are.  A wily hacker could attack your site by sending a CGI script a huge POST of many megabytes.
       will attempt to read the entire POST into a variable, growing hugely in size until it runs out of memory.
       While the script attempts to allocate the memory the system may slow down dramatically.  This is a form of
       denial of service attack.

       Another possible attack is for the remote user to force to accept a huge file upload. will
       accept the upload and store it in a temporary directory even if your script doesn't expect to receive an
       uploaded file. will delete the file automatically when it terminates, but in the meantime the remote
       user may have filled up the server's disk space, causing problems for other programs.

       The best way to avoid denial of service attacks is to limit the amount of memory, CPU time and disk space that
       CGI scripts can use.  Some Web servers come with built-in facilities to accomplish this. In other cases, you
       can use the shell limit or ulimit commands to put ceilings on CGI resource usage. also has some simple built-in protections against denial of service attacks, but you must activate them
       before you can use them.  These take the form of two global variables in the CGI name space:

           If set to a non-negative integer, this variable puts a ceiling on the size of POSTings, in bytes.  If
  detects a POST that is greater than the ceiling, it will immediately exit with an error message.
           This value will affect both ordinary POSTs and multipart POSTs, meaning that it limits the maximum size of
           file uploads as well.  You should set this to a reasonably high value, such as 1 megabyte.

           If set to a non-zero value, this will disable file uploads completely.  Other fill-out form values will
           work as usual.

       You can use these variables in either of two ways.

       1. On a script-by-script basis
           Set the variable at the top of the script, right after the "use" statement:

               use CGI qw/:standard/;
               use CGI::Carp 'fatalsToBrowser';
               $CGI::POST_MAX=1024 * 100;  # max 100K posts
               $CGI::DISABLE_UPLOADS = 1;  # no uploads

       2. Globally for all scripts
           Open up, find the definitions for $POST_MAX and $DISABLE_UPLOADS, and set them to the desired val-
           ues.  You'll find them towards the top of the file in a subroutine named initialize_globals().

       An attempt to send a POST larger than $POST_MAX bytes will cause param() to return an empty CGI parameter list.
       You can test for this event by checking cgi_error(), either after you create the CGI object or, if you are
       using the function-oriented interface, call <param()> for the first time.  If the POST was intercepted, then
       cgi_error() will return the message "413 POST too large".

       This error message is actually defined by the HTTP protocol, and is designed to be returned to the browser as
       the CGI script's status
        code.  For example:

          $uploaded_file = param('upload');
          if (!$uploaded_file && cgi_error()) {
             print header(-status=>cgi_error());
             exit 0;

       However it isn't clear that any browser currently knows what to do with this status code.  It might be better
       just to create an HTML page that warns the user of the problem.

       To make it easier to port existing programs that use the compatibility routine "ReadParse" is pro-
       vided.  Porting is simple:

           require "";
           print "The value of the antique is $in{antique}.\n";

           use CGI;
           print "The value of the antique is $in{antique}.\n";'s ReadParse() routine creates a tied variable named %in, which can be accessed to obtain the query vari-
       ables.  Like ReadParse, you can also provide your own variable.  Infrequently used features of ReadParse, such
       as the creation of @in and $in variables, are not supported.

       Once you use ReadParse, you can retrieve the query object itself this way:

           $q = $in{CGI};
           print textfield(-name=>'wow',
                               -value=>'does this really work?');

       This allows you to start using the more interesting features of without rewriting your old scripts from

       Copyright 1995-1998, Lincoln D. Stein.  All rights reserved.

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       Address bug reports and comments to:  When sending bug reports, please provide the version of, the version of Perl, the name and version of your Web server, and the name and version of the operating
       system you are using.  If the problem is even remotely browser dependent, please provide information about the
       affected browers as well.

       Thanks very much to:

       Matt Heffron (
       James Taylor (
       Scott Anguish <>
       Mike Jewell (
       Timothy Shimmin (
       Joergen Haegg (
       Laurent Delfosse (
       Richard Resnick (
       Craig Bishop (
       Tony Curtis (
       Tim Bunce (
       Tom Christiansen (
       Andreas Koenig (kATfranz.DE)
       Tim MacKenzie (
       Kevin B. Hendricks (
       Stephen Dahmen (
       Ed Jordan (
       David Alan Pisoni (
       Doug MacEachern (
       Robin Houston (
       ...and many many more...
           for suggestions and bug fixes.


               use CGI ':standard';

               print header;
               print start_html("Example Form");
               print "<h1> Example Form</h1>\n";
               print end_html;

               sub print_prompt {
                  print start_form;
                  print "<em>What's your name?</em><br>";
                  print textfield('name');
                  print checkbox('Not my real name');

                  print "<p><em>Where can you find English Sparrows?</em><br>";
                  print checkbox_group(
                                        -name=>'Sparrow locations',

                  print "<p><em>How far can they fly?</em><br>",
                               -name=>'how far',
                               -values=>['10 ft','1 mile','10 miles','real far'],
                               -default=>'1 mile');

                  print "<p><em>What's your favorite color?</em>  ";
                  print popup_menu(-name=>'Color',

                  print hidden('Reference','Monty Python and the Holy Grail');

                  print "<p><em>What have you got there?</em><br>";
                  print scrolling_list(
                                -values=>['A Coconut','A Grail','An Icon',
                                          'A Sword','A Ticket'],

                  print "<p><em>Any parting comments?</em><br>";
                  print textarea(-name=>'Comments',

                  print "<p>",reset;
                  print submit('Action','Shout');
                  print submit('Action','Scream');
                  print endform;
                  print "<hr>\n";

               sub do_work {

                  print "<h2>Here are the current settings in this form</h2>";

                  foreach $key (param) {
                     print "<strong>$key</strong> -> ";
                     @values = param($key);
                     print join(", ",@values),"<br>\n";

               sub print_tail {
                  print <<END;
               <address>Lincoln D. Stein</address><br>
               <a href="/">Home Page</a>

       Please report them.

       CGI::Carp, CGI::Fast, CGI::Pretty

perl v5.8.8                       2001-09-21                            CGI(3)