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CPAN(3)               User Contributed Perl Documentation              CPAN(3)

       CPAN - query, download and build perl modules from CPAN sites

       Interactive mode:

         perl -MCPAN -e shell



       Basic commands:

         # Modules:

         cpan> install Acme::Meta                       # in the shell

         CPAN::Shell->install("Acme::Meta");            # in perl

         # Distributions:

         cpan> install NWCLARK/Acme-Meta-0.02.tar.gz    # in the shell

           install("NWCLARK/Acme-Meta-0.02.tar.gz");    # in perl

         # module objects:

         $mo = CPAN::Shell->expandany($mod);
         $mo = CPAN::Shell->expand("Module",$mod);      # same thing

         # distribution objects:

         $do = CPAN::Shell->expand("Module",$mod)->distribution;
         $do = CPAN::Shell->expandany($distro);         # same thing
         $do = CPAN::Shell->expand("Distribution",
                                   $distro);            # same thing

       The CPAN module automates or at least simplifies the make and install of perl modules and extensions. It
       includes some primitive searching capabilities and knows how to use Net::FTP or LWP or some external download
       clients to fetch the distributions from the net.

       These are fetched from one or more of the mirrored CPAN (Comprehensive Perl Archive Network) sites and unpacked
       in a dedicated directory.

       The CPAN module also supports the concept of named and versioned bundles of modules. Bundles simplify the han-
       dling of sets of related modules. See Bundles below.

       The package contains a session manager and a cache manager. The session manager keeps track of what has been
       fetched, built and installed in the current session. The cache manager keeps track of the disk space occupied
       by the make processes and deletes excess space according to a simple FIFO mechanism.

       All methods provided are accessible in a programmer style and in an interactive shell style.

       CPAN::shell([$prompt, $command]) Starting Interactive Mode

       The interactive mode is entered by running

           perl -MCPAN -e shell



       which puts you into a readline interface. If "Term::ReadKey" and either "Term::ReadLine::Perl" or "Term::Read-
       Line::Gnu" are installed it supports both history and command completion.

       Once you are on the command line, type "h" to get a one page help screen and the rest should be self-explana-

       The function call "shell" takes two optional arguments, one is the prompt, the second is the default initial
       command line (the latter only works if a real ReadLine interface module is installed).

       The most common uses of the interactive modes are

       Searching for authors, bundles, distribution files and modules
         There are corresponding one-letter commands "a", "b", "d", and "m" for each of the four categories and
         another, "i" for any of the mentioned four. Each of the four entities is implemented as a class with slightly
         differing methods for displaying an object.

         Arguments you pass to these commands are either strings exactly matching the identification string of an
         object or regular expressions that are then matched case-insensitively against various attributes of the
         objects. The parser recognizes a regular expression only if you enclose it between two slashes.

         The principle is that the number of found objects influences how an item is displayed. If the search finds
         one item, the result is displayed with the rather verbose method "as_string", but if we find more than one,
         we display each object with the terse method "as_glimpse".


           cpan> m Acme::MetaSyntactic
           Module id = Acme::MetaSyntactic
               CPAN_USERID  BOOK (Philippe Bruhat (BooK) <[...]>)
               CPAN_VERSION 0.99
               CPAN_FILE    B/BO/BOOK/Acme-MetaSyntactic-0.99.tar.gz
               UPLOAD_DATE  2006-11-06
               MANPAGE      Acme::MetaSyntactic - Themed metasyntactic variables names
               INST_FILE    /usr/local/lib/perl/5.10.0/Acme/
               INST_VERSION 0.99
           cpan> a BOOK
           Author id = BOOK
               EMAIL        [...]
               FULLNAME     Philippe Bruhat (BooK)
           cpan> d BOOK/Acme-MetaSyntactic-0.99.tar.gz
           Distribution id = B/BO/BOOK/Acme-MetaSyntactic-0.99.tar.gz
               CPAN_USERID  BOOK (Philippe Bruhat (BooK) <[...]>)
               CONTAINSMODS Acme::MetaSyntactic Acme::MetaSyntactic::Alias [...]
               UPLOAD_DATE  2006-11-06
           cpan> m /lorem/
           Module  = Acme::MetaSyntactic::loremipsum (BOOK/Acme-MetaSyntactic-0.99.tar.gz)
           Module    Text::Lorem            (ADEOLA/Text-Lorem-0.3.tar.gz)
           Module    Text::Lorem::More      (RKRIMEN/Text-Lorem-More-0.12.tar.gz)
           Module    Text::Lorem::More::Source (RKRIMEN/Text-Lorem-More-0.12.tar.gz)
           cpan> i /berlin/
           Distribution    BEATNIK/Filter-NumberLines-0.02.tar.gz
           Module  = DateTime::TimeZone::Europe::Berlin (DROLSKY/DateTime-TimeZone-0.7904.tar.gz)
           Module    Filter::NumberLines    (BEATNIK/Filter-NumberLines-0.02.tar.gz)
           Author          [...]

         The examples illustrate several aspects: the first three queries target modules, authors, or distros directly
         and yield exactly one result. The last two use regular expressions and yield several results. The last one
         targets all of bundles, modules, authors, and distros simultaneously. When more than one result is available,
         they are printed in one-line format.

       "get", "make", "test", "install", "clean" modules or distributions
         These commands take any number of arguments and investigate what is necessary to perform the action. If the
         argument is a distribution file name (recognized by embedded slashes), it is processed. If it is a module,
         CPAN determines the distribution file in which this module is included and processes that, following any
         dependencies named in the module's META.yml or Makefile.PL (this behavior is controlled by the configuration
         parameter "prerequisites_policy".)

         "get" downloads a distribution file and untars or unzips it, "make" builds it, "test" runs the test suite,
         and "install" installs it.

         Any "make" or "test" are run unconditionally. An

           install <distribution_file>

         also is run unconditionally. But for

           install <module>

         CPAN checks if an install is actually needed for it and prints module up to date in the case that the distri-
         bution file containing the module doesn't need to be updated.

         CPAN also keeps track of what it has done within the current session and doesn't try to build a package a
         second time regardless if it succeeded or not. It does not repeat a test run if the test has been run suc-
         cessfully before. Same for install runs.

         The "force" pragma may precede another command (currently: "get", "make", "test", or "install") and executes
         the command from scratch and tries to continue in case of some errors. See the section below on the "force"
         and the "fforce" pragma.

         The "notest" pragma may be used to skip the test part in the build process.


             cpan> notest install Tk

         A "clean" command results in a

           make clean

         being executed within the distribution file's working directory.

       "readme", "perldoc", "look" module or distribution
         "readme" displays the README file of the associated distribution.  "Look" gets and untars (if not yet done)
         the distribution file, changes to the appropriate directory and opens a subshell process in that directory.
         "perldoc" displays the pod documentation of the module in html or plain text format.

       "ls" author
       "ls" globbing_expression
         The first form lists all distribution files in and below an author's CPAN directory as they are stored in the
         CHECKUMS files distributed on CPAN. The listing goes recursive into all subdirectories.

         The second form allows to limit or expand the output with shell globbing as in the following examples:

               ls JV/make*
               ls GSAR/*make*
               ls */*make*

         The last example is very slow and outputs extra progress indicators that break the alignment of the result.

         Note that globbing only lists directories explicitly asked for, for example FOO/* will not list
         FOO/bar/Acme-Sthg-n.nn.tar.gz. This may be regarded as a bug and may be changed in future versions.

         The "failed" command reports all distributions that failed on one of "make", "test" or "install" for some
         reason in the currently running shell session.

       Persistence between sessions
         If the "YAML" or the "YAML::Syck" module is installed a record of the internal state of all modules is writ-
         ten to disk after each step.  The files contain a signature of the currently running perl version for later

         If the configurations variable "build_dir_reuse" is set to a true value, then reads the collected
         YAML files. If the stored signature matches the currently running perl the stored state is loaded into memory
         such that effectively persistence between sessions is established.

       The "force" and the "fforce" pragma
         To speed things up in complex installation scenarios, keeps track of what it has already done and
         refuses to do some things a second time. A "get", a "make", and an "install" are not repeated.  A "test" is
         only repeated if the previous test was unsuccessful. The diagnostic message when refuses to do some-
         thing a second time is one of Has already been "unwrapped|made|tested successfully" or something similar.
         Another situation where CPAN refuses to act is an "install" if the according "test" was not successful.

         In all these cases, the user can override the goatish behaviour by prepending the command with the word
         force, for example:

           cpan> force get Foo
           cpan> force make AUTHOR/Bar-3.14.tar.gz
           cpan> force test Baz
           cpan> force install Acme::Meta

         Each forced command is executed with the according part of its memory erased.

         The "fforce" pragma is a variant that emulates a "force get" which erases the entire memory followed by the
         action specified, effectively restarting the whole get/make/test/install procedure from scratch.

         Interactive sessions maintain a lockfile, per default "~/.cpan/.lock".  Batch jobs can run without a lockfile
         and do not disturb each other.

         The shell offers to run in degraded mode when another process is holding the lockfile. This is an experimen-
         tal feature that is not yet tested very well. This second shell then does not write the history file, does
         not use the metadata file and has a different prompt.

       Signals installs signal handlers for SIGINT and SIGTERM. While you are in the cpan-shell it is intended that
         you can press "^C" anytime and return to the cpan-shell prompt. A SIGTERM will cause the cpan-shell to clean
         up and leave the shell loop. You can emulate the effect of a SIGTERM by sending two consecutive SIGINTs,
         which usually means by pressing "^C" twice.
 ignores a SIGPIPE. If the user sets "inactivity_timeout", a SIGALRM is used during the run of the
         "perl Makefile.PL" or "perl Build.PL" subprocess.


       The commands that are available in the shell interface are methods in the package CPAN::Shell. If you enter the
       shell command, all your input is split by the Text::ParseWords::shellwords() routine which acts like most
       shells do. The first word is being interpreted as the method to be called and the rest of the words are treated
       as arguments to this method. Continuation lines are supported if a line ends with a literal backslash.


       "autobundle" writes a bundle file into the "$CPAN::Config->{cpan_home}/Bundle" directory. The file contains a
       list of all modules that are both available from CPAN and currently installed within @INC. The name of the bun-
       dle file is based on the current date and a counter.


       Note: this feature is still in alpha state and may change in future versions of

       This commands provides a statistical overview over recent download activities. The data for this is collected
       in the YAML file "FTPstats.yml" in your "cpan_home" directory. If no YAML module is configured or YAML not
       installed, then no stats are provided.


       mkmyconfig() writes your own CPAN::MyConfig file into your ~/.cpan/ directory so that you can save your own
       preferences instead of the system wide ones.

       recent ***EXPERIMENTAL COMMAND***

       The "recent" command downloads a list of recent uploads to CPAN and displays them slowly. While the command is
       running $SIG{INT} is defined to mean that the loop shall be left after having displayed the current item.

       Note: This command requires XML::LibXML installed.

       Note: This whole command currently is just a hack and will probably change in future versions of but
       the general approach will likely stay.

       Note: See also smoke


       recompile() is a very special command in that it takes no argument and runs the make/test/install cycle with
       brute force over all installed dynamically loadable extensions (aka XS modules) with 'force' in effect. The
       primary purpose of this command is to finish a network installation. Imagine, you have a common source tree for
       two different architectures. You decide to do a completely independent fresh installation. You start on one
       architecture with the help of a Bundle file produced earlier. CPAN installs the whole Bundle for you, but when
       you try to repeat the job on the second architecture, CPAN responds with a "Foo up to date" message for all
       modules. So you invoke CPAN's recompile on the second architecture and you're done.

       Another popular use for "recompile" is to act as a rescue in case your perl breaks binary compatibility. If one
       of the modules that CPAN uses is in turn depending on binary compatibility (so you cannot run CPAN commands),
       then you should try the CPAN::Nox module for recovery.

       report Bundle|Distribution|Module

       The "report" command temporarily turns on the "test_report" config variable, then runs the "force test" command
       with the given arguments. The "force" pragma is used to re-run the tests and repeat every step that might have
       failed before.

       smoke ***EXPERIMENTAL COMMAND***

       *** WARNING: this command downloads and executes software from CPAN to your computer of completely unknown sta-
       tus. You should never do this with your normal account and better have a dedicated well separated and secured
       machine to do this. ***

       The "smoke" command takes the list of recent uploads to CPAN as provided by the "recent" command and tests them
       all. While the command is running $SIG{INT} is defined to mean that the current item shall be skipped.

       Note: This whole command currently is just a hack and will probably change in future versions of but
       the general approach will likely stay.

       Note: See also recent

       upgrade [Module|/Regex/]...

       The "upgrade" command first runs an "r" command with the given arguments and then installs the newest versions
       of all modules that were listed by that.

       The four "CPAN::*" Classes: Author, Bundle, Module, Distribution

       Although it may be considered internal, the class hierarchy does matter for both users and programmer.
       deals with above mentioned four classes, and all those classes share a set of methods. A classical single poly-
       morphism is in effect. A metaclass object registers all objects of all kinds and indexes them with a string.
       The strings referencing objects have a separated namespace (well, not completely separated):

                Namespace                         Class

          words containing a "/" (slash)      Distribution
           words starting with Bundle::          Bundle
                 everything else            Module or Author

       Modules know their associated Distribution objects. They always refer to the most recent official release.
       Developers may mark their releases as unstable development versions (by inserting an underbar into the module
       version number which will also be reflected in the distribution name when you run 'make dist'), so the really
       hottest and newest distribution is not always the default.  If a module Foo circulates on CPAN in both version
       1.23 and 1.23_90, offers a convenient way to install version 1.23 by saying

           install Foo

       This would install the complete distribution file (say BAR/Foo-1.23.tar.gz) with all accompanying material. But
       if you would like to install version 1.23_90, you need to know where the distribution file resides on CPAN rel-
       ative to the authors/id/ directory. If the author is BAR, this might be BAR/Foo-1.23_90.tar.gz; so you would
       have to say

           install BAR/Foo-1.23_90.tar.gz

       The first example will be driven by an object of the class CPAN::Module, the second by an object of class

       Integrating local directories

       Note: this feature is still in alpha state and may change in future versions of

       Distribution objects are normally distributions from the CPAN, but there is a slightly degenerate case for Dis-
       tribution objects, too, of projects held on the local disk. These distribution objects have the same name as
       the local directory and end with a dot. A dot by itself is also allowed for the current directory at the time was used. All actions such as "make", "test", and "install" are applied directly to that directory.
       This gives the command "cpan ." an interesting touch: while the normal mantra of installing a CPAN module with-
       out is one of

           perl Makefile.PL                 perl Build.PL
                  ( go and get prerequisites )
           make                             ./Build
           make test                        ./Build test
           make install                     ./Build install

       the command "cpan ." does all of this at once. It figures out which of the two mantras is appropriate, fetches
       and installs all prerequisites, cares for them recursively and finally finishes the installation of the module
       in the current directory, be it a CPAN module or not.

       The typical usage case is for private modules or working copies of projects from remote repositories on the
       local disk.


       The usual shell redirection symbols " | " and ">" are recognized by the cpan shell when surrounded by whites-
       pace. So piping into a pager and redirecting output into a file works quite similar to any shell.

       When the CPAN module is used for the first time, a configuration dialog tries to determine a couple of site
       specific options. The result of the dialog is stored in a hash reference  $CPAN::Config in a file CPAN/Con-

       The default values defined in the CPAN/ file can be overridden in a user specific file: CPAN/MyCon- Such a file is best placed in $HOME/.cpan/CPAN/, because $HOME/.cpan is added to the search
       path of the CPAN module before the use() or require() statements. The mkmyconfig command writes this file for

       The "o conf" command has various bells and whistles:

       completion support
           If you have a ReadLine module installed, you can hit TAB at any point of the commandline and "o conf" will
           offer you completion for the built-in subcommands and/or config variable names.

       displaying some help: o conf help
           Displays a short help

       displaying current values: o conf [KEY]
           Displays the current value(s) for this config variable. Without KEY displays all subcommands and config


             o conf shell

           If KEY starts and ends with a slash the string in between is interpreted as a regular expression and only
           keys matching this regex are displayed


             o conf /color/

       changing of scalar values: o conf KEY VALUE
           Sets the config variable KEY to VALUE. The empty string can be specified as usual in shells, with '' or ""


             o conf wget /usr/bin/wget

       changing of list values: o conf KEY SHIFT|UNSHIFT|PUSH|POP|SPLICE|LIST
           If a config variable name ends with "list", it is a list. "o conf KEY shift" removes the first element of
           the list, "o conf KEY pop" removes the last element of the list. "o conf KEYS unshift LIST" prepends a list
           of values to the list, "o conf KEYS push LIST" appends a list of valued to the list.

           Likewise, "o conf KEY splice LIST" passes the LIST to the according splice command.

           Finally, any other list of arguments is taken as a new list value for the KEY variable discarding the pre-
           vious value.


             o conf urllist unshift
             o conf urllist splice 3 1
             o conf urllist http://cpan1.local http://cpan2.local

       reverting to saved: o conf defaults
           Reverts all config variables to the state in the saved config file.

       saving the config: o conf commit
           Saves all config variables to the current config file (CPAN/ or CPAN/ that was loaded
           at start).

       The configuration dialog can be started any time later again by issuing the command " o conf init " in the CPAN
       shell. A subset of the configuration dialog can be run by issuing "o conf init WORD" where WORD is any valid
       config variable or a regular expression.

       Config Variables

       Currently the following keys in the hash reference $CPAN::Config are defined:

         applypatch         path to external prg
         auto_commit        commit all changes to config variables to disk
         build_cache        size of cache for directories to build modules
         build_dir          locally accessible directory to build modules
         build_dir_reuse    boolean if distros in build_dir are persistent
                            to install or not to install when a module is
                            only needed for building. yes|no|ask/yes|ask/no
         bzip2              path to external prg
         cache_metadata     use serializer to cache metadata
         check_sigs         if signatures should be verified
         colorize_debug     Term::ANSIColor attributes for debugging output
         colorize_output    boolean if Term::ANSIColor should colorize output
         colorize_print     Term::ANSIColor attributes for normal output
         colorize_warn      Term::ANSIColor attributes for warnings
                            boolean if you want to see current command number
         commands_quote     prefered character to use for quoting external
                            commands when running them. Defaults to double
                            quote on Windows, single tick everywhere else;
                            can be set to space to disable quoting
                            if we shall ask if opening a connection is ok before
                            urllist is specified
         cpan_home          local directory reserved for this package
         curl               path to external prg
         dontload_hash      DEPRECATED
         dontload_list      arrayref: modules in the list will not be
                            loaded by the CPAN::has_inst() routine
         ftp                path to external prg
         ftp_passive        if set, the envariable FTP_PASSIVE is set for downloads
         ftp_proxy          proxy host for ftp requests
         ftpstats_period    max number of days to keep download statistics
         ftpstats_size      max number of items to keep in the download statistics
         getcwd             see below
         gpg                path to external prg
         gzip               location of external program gzip
         halt_on_failure    stop processing after the first failure of queued
                            items or dependencies
         histfile           file to maintain history between sessions
         histsize           maximum number of lines to keep in histfile
         http_proxy         proxy host for http requests
         inactivity_timeout breaks interactive Makefile.PLs or Build.PLs
                            after this many seconds inactivity. Set to 0 to
                            never break.
         index_expire       after this many days refetch index files
                            if true, does not print the startup message
         keep_source_where  directory in which to keep the source (if we do)
                            report loading of optional modules used by
         lynx               path to external prg
         make               location of external make program
         make_arg           arguments that should always be passed to 'make'
                            the make command for running 'make install', for
                            example 'sudo make'
         make_install_arg   same as make_arg for 'make install'
         makepl_arg         arguments passed to 'perl Makefile.PL'
         mbuild_arg         arguments passed to './Build'
         mbuild_install_arg arguments passed to './Build install'
                            command to use instead of './Build' when we are
                            in the install stage, for example 'sudo ./Build'
         mbuildpl_arg       arguments passed to 'perl Build.PL'
         ncftp              path to external prg
         ncftpget           path to external prg
         no_proxy           don't proxy to these hosts/domains (comma separated list)
         pager              location of external program more (or any pager)
         password           your password if you CPAN server wants one
         patch              path to external prg
         perl5lib_verbosity verbosity level for PERL5LIB additions
         prefer_installer   legal values are MB and EUMM: if a module comes
                            with both a Makefile.PL and a Build.PL, use the
                            former (EUMM) or the latter (MB); if the module
                            comes with only one of the two, that one will be
                            used in any case
                            what to do if you are missing module prerequisites
                            ('follow' automatically, 'ask' me, or 'ignore')
         prefs_dir          local directory to store per-distro build options
         proxy_user         username for accessing an authenticating proxy
         proxy_pass         password for accessing an authenticating proxy
         randomize_urllist  add some randomness to the sequence of the urllist
         scan_cache         controls scanning of cache ('atstart' or 'never')
         shell              your favorite shell
                            boolean if r command tells which modules are versionless
         show_upload_date   boolean if commands should try to determine upload date
         show_zero_versions boolean if r command tells for which modules $version==0
         tar                location of external program tar
         tar_verbosity      verbosity level for the tar command
         term_is_latin      deprecated: if true Unicode is translated to ISO-8859-1
                            (and nonsense for characters outside latin range)
         term_ornaments     boolean to turn ReadLine ornamenting on/off
         test_report        email test reports (if CPAN::Reporter is installed)
                            skip testing when previously tested ok (according to
                            CPAN::Reporter history)
         unzip              location of external program unzip
         urllist            arrayref to nearby CPAN sites (or equivalent locations)
         use_sqlite         use CPAN::SQLite for metadata storage (fast and lean)
         username           your username if you CPAN server wants one
         wait_list          arrayref to a wait server to try (See CPAN::WAIT)
         wget               path to external prg
         yaml_load_code     enable YAML code deserialisation via CPAN::DeferedCode
         yaml_module        which module to use to read/write YAML files

       You can set and query each of these options interactively in the cpan shell with the "o conf" or the "o conf
       init" command as specified below.

       "o conf <scalar option>"
         prints the current value of the scalar option

       "o conf <scalar option> <value>"
         Sets the value of the scalar option to value

       "o conf <list option>"
         prints the current value of the list option in MakeMaker's neatvalue format.

       "o conf <list option> [shift|pop]"
         shifts or pops the array in the list option variable

       "o conf <list option> [unshift|push|splice] <list>"
         works like the corresponding perl commands.

       interactive editing: o conf init [MATCH|LIST]
         Runs an interactive configuration dialog for matching variables.  Without argument runs the dialog over all
         supported config variables.  To specify a MATCH the argument must be enclosed by slashes.


           o conf init ftp_passive ftp_proxy
           o conf init /color/

         Note: this method of setting config variables often provides more explanation about the functioning of a
         variable than the manpage.

       CPAN::anycwd($path): Note on config variable getcwd changes the current working directory often and needs to determine its own current working directory.
       Per default it uses Cwd::cwd but if this doesn't work on your system for some reason, alternatives can be con-
       figured according to the following table:

       cwd Calls Cwd::cwd

           Calls Cwd::getcwd

           Calls Cwd::fastcwd

           Calls the external command cwd.

       Note on the format of the urllist parameter

       urllist parameters are URLs according to RFC 1738. We do a little guessing if your URL is not compliant, but if
       you have problems with "file" URLs, please try the correct format. Either:




       The urllist parameter has CD-ROM support

       The "urllist" parameter of the configuration table contains a list of URLs that are to be used for downloading.
       If the list contains any "file" URLs, CPAN always tries to get files from there first. This feature is disabled
       for index files. So the recommendation for the owner of a CD-ROM with CPAN contents is: include your local,
       possibly outdated CD-ROM as a "file" URL at the end of urllist, e.g.

         o conf urllist push file://localhost/CDROM/CPAN will then fetch the index files from one of the CPAN sites that come at the beginning of urllist. It
       will later check for each module if there is a local copy of the most recent version.

       Another peculiarity of urllist is that the site that we could successfully fetch the last file from automati-
       cally gets a preference token and is tried as the first site for the next request. So if you add a new site at
       runtime it may happen that the previously preferred site will be tried another time. This means that if you
       want to disallow a site for the next transfer, it must be explicitly removed from urllist.

       Maintaining the urllist parameter

       If you have (or some other YAML module configured in "yaml_module") installed, collects a few
       statistical data about recent downloads. You can view the statistics with the "hosts" command or inspect them
       directly by looking into the "FTPstats.yml" file in your "cpan_home" directory.

       To get some interesting statistics it is recommended to set the "randomize_urllist" parameter that introduces
       some amount of randomness into the URL selection.

       The "requires" and "build_requires" dependency declarations

       Since version 1.88_51 modules declared as "build_requires" by a distribution are treated differently
       depending on the config variable "build_requires_install_policy". By setting "build_requires_install_policy" to
       "no" such a module is not being installed. It is only built and tested and then kept in the list of tested but
       uninstalled modules. As such it is available during the build of the dependent module by integrating the path
       to the "blib/arch" and "blib/lib" directories in the environment variable PERL5LIB. If
       "build_requires_install_policy" is set ti "yes", then both modules declared as "requires" and those declared as
       "build_requires" are treated alike. By setting to "ask/yes" or "ask/no", asks the user and sets the
       default accordingly.

       Configuration for individual distributions (Distroprefs)

       (Note: This feature has been introduced in 1.8854 and is still considered beta quality)

       Distributions on the CPAN usually behave according to what we call the CPAN mantra. Or since the event of Mod-
       ule::Build we should talk about two mantras:

           perl Makefile.PL     perl Build.PL
           make                 ./Build
           make test            ./Build test
           make install         ./Build install

       But some modules cannot be built with this mantra. They try to get some extra data from the user via the envi-
       ronment, extra arguments or interactively thus disturbing the installation of large bundles like Phalanx100 or
       modules with many dependencies like Plagger.

       The distroprefs system of "" addresses this problem by allowing the user to specify extra informations
       and recipes in YAML files to either

       ?   pass additional arguments to one of the four commands,

       ?   set environment variables

       ?   instantiate an Expect object that reads from the console, waits for some regular expressions and enters
           some answers

       ?   temporarily override assorted "" configuration variables

       ?   specify dependencies that the original maintainer forgot to specify

       ?   disable the installation of an object altogether

       See the YAML and Data::Dumper files that come with the "" distribution in the "distroprefs/" directory
       for examples.


       The YAML files themselves must have the ".yml" extension, all other files are ignored (for two exceptions see
       Fallback Data::Dumper and Storable below). The containing directory can be specified in "" in the
       "prefs_dir" config variable. Try "o conf init prefs_dir" in the CPAN shell to set and activate the distroprefs

       Every YAML file may contain arbitrary documents according to the YAML specification and every single document
       is treated as an entity that can specify the treatment of a single distribution.

       The names of the files can be picked freely, "" always reads all files (in alphabetical order) and takes
       the key "match" (see below in Language Specs) as a hashref containing match criteria that determine if the cur-
       rent distribution matches the YAML document or not.

       Fallback Data::Dumper and Storable

       If neither your configured "yaml_module" nor is installed falls back to using Data::Dumper and
       Storable and looks for files with the extensions ".dd" or ".st" in the "prefs_dir" directory. These files are
       expected to contain one or more hashrefs.  For Data::Dumper generated files, this is expected to be done with
       by defining $VAR1, $VAR2, etc. The YAML shell would produce these with the command

           ysh < somefile.yml > somefile.dd

       For Storable files the rule is that they must be constructed such that "Storable::retrieve(file)" returns an
       array reference and the array elements represent one distropref object each. The conversion from YAML would
       look like so:

           perl -MYAML=LoadFile -MStorable=nstore -e '
               nstore(\@y, shift)' somefile.yml

       In bootstrapping situations it is usually sufficient to translate only a few YAML files to Data::Dumper for the
       crucial modules like "YAML::Syck", "" and "". If you prefer Storable over Data::Dumper, remem-
       ber to pull out a Storable version that writes an older format than all the other Storable versions that will
       need to read them.


       The following example contains all supported keywords and structures with the exception of "eexpect" which can
       be used instead of "expect".

         comment: "Demo"
           module: "Dancing::Queen"
           distribution: "^CHACHACHA/Dancing-"
           perl: "/usr/local/cariba-perl/bin/perl"
             archname: "freebsd"
             DANCING_FLOOR: "Shubiduh"
         disabled: 1
           make: gmake
             - "--somearg=specialcase"

           env: {}

             - "Which is your favorite fruit"
             - "apple\n"

             - all
             - extra-all

           env: {}

           expect: []

           commendline: "echo SKIPPING make"

           args: []

           env: {}

           expect: []

           args: []

             WANT_TO_INSTALL: YES

             - "Do you really want to install"
             - "y\n"

           - "ABCDE/Fedcba-3.14-ABCDE-01.patch"

             LWP: 5.8
             Test::Exception: 0.25
             Spiffy: 0.30

       Language Specs

       Every YAML document represents a single hash reference. The valid keys in this hash are as follows:

       comment [scalar]
           A comment

       cpanconfig [hash]
           Temporarily override assorted "" configuration variables.

           Supported are: "build_requires_install_policy", "check_sigs", "make", "make_install_make_command", "pre-
           fer_installer", "test_report". Please report as a bug when you need another one supported.

       depends [hash] *** EXPERIMENTAL FEATURE ***
           All three types, namely "configure_requires", "build_requires", and "requires" are supported in the way
           specified in the META.yml specification. The current implementation merges the specified dependencies with
           those declared by the package maintainer. In a future implementation this may be changed to override the
           original declaration.

       disabled [boolean]
           Specifies that this distribution shall not be processed at all.

       features [array] *** EXPERIMENTAL FEATURE ***
           Experimental implementation to deal with optional_features from META.yml. Still needs coordination with
           installer software and currently only works for META.yml declaring "dynamic_config=0". Use with caution.

       goto [string]
           The canonical name of a delegate distribution that shall be installed instead. Useful when a new version,
           although it tests OK itself, breaks something else or a developer release or a fork is already uploaded
           that is better than the last released version.

       install [hash]
           Processing instructions for the "make install" or "./Build install" phase of the CPAN mantra. See below
           under Processing Instructions.

       make [hash]
           Processing instructions for the "make" or "./Build" phase of the CPAN mantra. See below under Processing

       match [hash]
           A hashref with one or more of the keys "distribution", "modules", "perl", "perlconfig", and "env" that
           specify if a document is targeted at a specific CPAN distribution or installation.

           The corresponding values are interpreted as regular expressions. The "distribution" related one will be
           matched against the canonical distribution name, e.g. "AUTHOR/Foo-Bar-3.14.tar.gz".

           The "module" related one will be matched against all modules contained in the distribution until one module

           The "perl" related one will be matched against $^X (but with the absolute path).

           The value associated with "perlconfig" is itself a hashref that is matched against corresponding values in
           the %Config::Config hash living in the "" module.

           The value associated with "env" is itself a hashref that is matched against corresponding values in the
           %ENV hash.

           If more than one restriction of "module", "distribution", etc. is specified, the results of the separately
           computed match values must all match. If this is the case then the hashref represented by the YAML document
           is returned as the preference structure for the current distribution.

       patches [array]
           An array of patches on CPAN or on the local disk to be applied in order via the external patch program. If
           the value for the "-p" parameter is 0 or 1 is determined by reading the patch beforehand.

           Note: if the "applypatch" program is installed and "CPAN::Config" knows about it and a patch is written by
           the "makepatch" program, then "" lets "applypatch" apply the patch. Both "makepatch" and "apply-
           patch" are available from CPAN in the "JV/makepatch-*" distribution.

       pl [hash]
           Processing instructions for the "perl Makefile.PL" or "perl Build.PL" phase of the CPAN mantra. See below
           under Processing Instructions.

       test [hash]
           Processing instructions for the "make test" or "./Build test" phase of the CPAN mantra. See below under
           Processing Instructions.

       Processing Instructions

       args [array]
           Arguments to be added to the command line

           A full commandline that will be executed as it stands by a system call. During the execution the environ-
           ment variable PERL will is set to $^X (but with an absolute path). If "commandline" is specified, the
           content of "args" is not used.

       eexpect [hash]
           Extended "expect". This is a hash reference with four allowed keys, "mode", "timeout", "reuse", and "talk".

           "mode" may have the values "deterministic" for the case where all questions come in the order written down
           and "anyorder" for the case where the questions may come in any order. The default mode is "deterministic".

           "timeout" denotes a timeout in seconds. Floating point timeouts are OK. In the case of a "mode=determinis-
           tic" the timeout denotes the timeout per question, in the case of "mode=anyorder" it denotes the timeout
           per byte received from the stream or questions.

           "talk" is a reference to an array that contains alternating questions and answers. Questions are regular
           expressions and answers are literal strings. The Expect module will then watch the stream coming from the
           execution of the external program ("perl Makefile.PL", "perl Build.PL", "make", etc.).

           In the case of "mode=deterministic" the will inject the according answer as soon as the stream
           matches the regular expression.

           In the case of "mode=anyorder" will answer a question as soon as the timeout is reached for the
           next byte in the input stream. In this mode you can use the "reuse" parameter to decide what shall happen
           with a question-answer pair after it has been used. In the default case (reuse=0) it is removed from the
           array, so it cannot be used again accidentally. In this case, if you want to answer the question "Do you
           really want to do that" several times, then it must be included in the array at least as often as you want
           this answer to be given. Setting the parameter "reuse" to 1 makes this repetition unnecessary.

       env [hash]
           Environment variables to be set during the command

       expect [array]
           "expect: <array>" is a short notation for

               mode: deterministic
               timeout: 15
               talk: <array>

       Schema verification with "Kwalify"

       If you have the "Kwalify" module installed (which is part of the Bundle::CPANxxl), then all your distroprefs
       files are checked for syntactical correctness.

       Example Distroprefs Files

       "" comes with a collection of example YAML files. Note that these are really just examples and should
       not be used without care because they cannot fit everybody's purpose. After all the authors of the packages
       that ask questions had a need to ask, so you should watch their questions and adjust the examples to your envi-
       ronment and your needs. You have beend warned:-)

       If you do not enter the shell, the available shell commands are both available as methods
       ("CPAN::Shell->install(...)") and as functions in the calling package ("install(...)").  Before calling low-
       level commands it makes sense to initialize components of CPAN you need, e.g.:


       High-level commands do such initializations automatically.

       There's currently only one class that has a stable interface - CPAN::Shell. All commands that are available in
       the CPAN shell are methods of the class CPAN::Shell. Each of the commands that produce listings of modules
       ("r", "autobundle", "u") also return a list of the IDs of all modules within the list.

         The IDs of all objects available within a program are strings that can be expanded to the corresponding real
         objects with the "CPAN::Shell->expand("Module",@things)" method. Expand returns a list of CPAN::Module
         objects according to the @things arguments given. In scalar context it only returns the first element of the

         Like expand, but returns objects of the appropriate type, i.e.  CPAN::Bundle objects for bundles, CPAN::Mod-
         ule objects for modules and CPAN::Distribution objects for distributions. Note: it does not expand to
         CPAN::Author objects.

       Programming Examples
         This enables the programmer to do operations that combine functionalities that are available in the shell.

             # install everything that is outdated on my disk:
             perl -MCPAN -e 'CPAN::Shell->install(CPAN::Shell->r)'

             # install my favorite programs if necessary:
             for $mod (qw(Net::FTP Digest::SHA Data::Dumper)) {

             # list all modules on my disk that have no VERSION number
             for $mod (CPAN::Shell->expand("Module","/./")) {
                 next unless $mod->inst_file;
                 # MakeMaker convention for undefined $VERSION:
                 next unless $mod->inst_version eq "undef";
                 print "No VERSION in ", $mod->id, "\n";

             # find out which distribution on CPAN contains a module:
             print CPAN::Shell->expand("Module","Apache::Constants")->cpan_file

         Or if you want to write a cronjob to watch The CPAN, you could list all modules that need updating. First a
         quick and dirty way:

             perl -e 'use CPAN; CPAN::Shell->r;'

         If you don't want to get any output in the case that all modules are up to date, you can parse the output of
         above command for the regular expression //modules are up to date// and decide to mail the output only if it
         doesn't match. Ick?

         If you prefer to do it more in a programmer style in one single process, maybe something like this suits you

           # list all modules on my disk that have newer versions on CPAN
           for $mod (CPAN::Shell->expand("Module","/./")) {
             next unless $mod->inst_file;
             next if $mod->uptodate;
             printf "Module %s is installed as %s, could be updated to %s from CPAN\n",
                 $mod->id, $mod->inst_version, $mod->cpan_version;

         If that gives you too much output every day, you maybe only want to watch for three modules. You can write

           for $mod (CPAN::Shell->expand("Module","/Apache|LWP|CGI/")) {

         as the first line instead. Or you can combine some of the above tricks:

           # watch only for a new mod_perl module
           $mod = CPAN::Shell->expand("Module","mod_perl");
           exit if $mod->uptodate;
           # new mod_perl arrived, let me know all update recommendations

       Methods in the other Classes

           Returns a one-line description of the author

           Returns a multi-line description of the author

           Returns the author's email address

           Returns the author's name

           An alias for fullname

           Returns a one-line description of the bundle

           Returns a multi-line description of the bundle

           Recursively runs the "clean" method on all items contained in the bundle.

           Returns a list of objects' IDs contained in a bundle. The associated objects may be bundles, modules or

           Forces CPAN to perform a task that it normally would have refused to do. Force takes as arguments a method
           name to be called and any number of additional arguments that should be passed to the called method.  The
           internals of the object get the needed changes so that does not refuse to take the action. The
           "force" is passed recursively to all contained objects. See also the section above on the "force" and the
           "fforce" pragma.

           Recursively runs the "get" method on all items contained in the bundle

           Returns the highest installed version of the bundle in either @INC or "$CPAN::Config-"{cpan_home}>. Note
           that this is different from CPAN::Module::inst_file.

           Like CPAN::Bundle::inst_file, but returns the $VERSION

           Returns 1 if the bundle itself and all its members are uptodate.

           Recursively runs the "install" method on all items contained in the bundle

           Recursively runs the "make" method on all items contained in the bundle

           Recursively runs the "readme" method on all items contained in the bundle

           Recursively runs the "test" method on all items contained in the bundle

           Returns a one-line description of the distribution

           Returns a multi-line description of the distribution

           Returns the CPAN::Author object of the maintainer who uploaded this distribution

           Returns a string of the form "AUTHORID/TARBALL", where AUTHORID is the author's PAUSE ID and TARBALL is the
           distribution filename.

           Returns the distribution filename without any archive suffix.  E.g "Foo-Bar-0.01"

           Changes to the directory where the distribution has been unpacked and runs "make clean" there.

           Returns a list of IDs of modules contained in a distribution file.  Only works for distributions listed in
           the 02packages.details.txt.gz file. This typically means that only the most recent version of a
           distribution is covered.

           Changes to the directory where the distribution has been unpacked and runs something like

               cvs -d $cvs_root import -m $cvs_log $cvs_dir $userid v$version


           Returns the directory into which this distribution has been unpacked.

           Forces CPAN to perform a task that it normally would have refused to do. Force takes as arguments a method
           name to be called and any number of additional arguments that should be passed to the called method.  The
           internals of the object get the needed changes so that does not refuse to take the action. See also
           the section above on the "force" and the "fforce" pragma.

           Downloads the distribution from CPAN and unpacks it. Does nothing if the distribution has already been
           downloaded and unpacked within the current session.

           Changes to the directory where the distribution has been unpacked and runs the external command "make
           install" there. If "make" has not yet been run, it will be run first. A "make test" will be issued in any
           case and if this fails, the install will be canceled. The cancellation can be avoided by letting "force"
           run the "install" for you.

           This install method has only the power to install the distribution if there are no dependencies in the way.
           To install an object and all of its dependencies, use CPAN::Shell->install.

           Note that install() gives no meaningful return value. See uptodate().

           Install all the distributions that have been tested sucessfully but not yet installed. See also

           Returns 1 if this distribution file seems to be a perl distribution.  Normally this is derived from the
           file name only, but the index from CPAN can contain a hint to achieve a return value of true for other
           filenames too.

           Changes to the directory where the distribution has been unpacked and opens a subshell there. Exiting the
           subshell returns.

           First runs the "get" method to make sure the distribution is downloaded and unpacked. Changes to the direc-
           tory where the distribution has been unpacked and runs the external commands "perl Makefile.PL" or "perl
           Build.PL" and "make" there.

           Downloads the pod documentation of the file associated with a distribution (in html format) and runs it
           through the external command lynx specified in "$CPAN::Config-"{lynx}>. If lynx isn't available, it con-
           verts it to plain text with external command html2text and runs it through the pager specified in

           Returns the hash reference from the first matching YAML file that the user has deposited in the
           "prefs_dir/" directory. The first succeeding match wins. The files in the "prefs_dir/" are processed alpha-
           betically and the canonical distroname (e.g.  AUTHOR/Foo-Bar-3.14.tar.gz) is matched against the regular
           expressions stored in the $root->{match}{distribution} attribute value.  Additionally all module names con-
           tained in a distribution are matched agains the regular expressions in the $root->{match}{module} attribute
           value. The two match values are ANDed together. Each of the two attributes are optional.

           Returns the hash reference that has been announced by a distribution as the the "requires" and
           "build_requires" elements. These can be declared either by the "META.yml" (if authoritative) or can be
           deposited after the run of "Build.PL" in the file "./_build/prereqs" or after the run of "Makfile.PL" writ-
           ten as the "PREREQ_PM" hash in a comment in the produced "Makefile". Note: this method only works after an
           attempt has been made to "make" the distribution. Returns undef otherwise.

           Downloads the README file associated with a distribution and runs it through the pager specified in

           Downloads report data for this distribution from and displays a subset of them.

           Returns the content of the META.yml of this distro as a hashref. Note: works only after an attempt has been
           made to "make" the distribution.  Returns undef otherwise. Also returns undef if the content of META.yml is
           not authoritative. (The rules about what exactly makes the content authoritative are still in flux.)

           Changes to the directory where the distribution has been unpacked and runs "make test" there.

           Returns 1 if all the modules contained in the distribution are uptodate. Relies on containsmods.

           Forces a reload of all indices.

           Reloads all indices if they have not been read for more than "$CPAN::Config-"{index_expire}> days.

           CPAN::Author, CPAN::Bundle, CPAN::Module, and CPAN::Distribution inherit this method. It prints the data
           structure associated with an object. Useful for debugging. Note: the data structure is considered internal
           and thus subject to change without notice.

           Returns a one-line description of the module in four columns: The first column contains the word "Module",
           the second column consists of one character: an equals sign if this module is already installed and upto-
           date, a less-than sign if this module is installed but can be upgraded, and a space if the module is not
           installed. The third column is the name of the module and the fourth column gives maintainer or distribu-
           tion information.

           Returns a multi-line description of the module

           Runs a clean on the distribution associated with this module.

           Returns the filename on CPAN that is associated with the module.

           Returns the latest version of this module available on CPAN.

           Runs a cvs_import on the distribution associated with this module.

           Returns a 44 character description of this module. Only available for modules listed in The Module List
           (CPAN/modules/00modlist.long.html or 00modlist.long.txt.gz)

           Returns the CPAN::Distribution object that contains the current version of this module.

           Returns a hash reference. The keys of the hash are the letters "D", "S", "L", "I", and <P>, for development
           status, support level, language, interface and public licence respectively. The data for the DSLIP status
           are collected by when authors register their namespaces. The values of the 5 hash elements
           are one-character words whose meaning is described in the table below. There are also 5 hash elements "DV",
           "SV", "LV", "IV", and <PV> that carry a more verbose value of the 5 status variables.

           Where the 'DSLIP' characters have the following meanings:

             D - Development Stage  (Note: *NO IMPLIED TIMESCALES*):
               i   - Idea, listed to gain consensus or as a placeholder
               c   - under construction but pre-alpha (not yet released)
               a/b - Alpha/Beta testing
               R   - Released
               M   - Mature (no rigorous definition)
               S   - Standard, supplied with Perl 5

             S - Support Level:
               m   - Mailing-list
               d   - Developer
               u   - Usenet newsgroup comp.lang.perl.modules
               n   - None known, try comp.lang.perl.modules
               a   - abandoned; volunteers welcome to take over maintainance

             L - Language Used:
               p   - Perl-only, no compiler needed, should be platform independent
               c   - C and perl, a C compiler will be needed
               h   - Hybrid, written in perl with optional C code, no compiler needed
               +   - C++ and perl, a C++ compiler will be needed
               o   - perl and another language other than C or C++

             I - Interface Style
               f   - plain Functions, no references used
               h   - hybrid, object and function interfaces available
               n   - no interface at all (huh?)
               r   - some use of unblessed References or ties
               O   - Object oriented using blessed references and/or inheritance

             P - Public License
               p   - Standard-Perl: user may choose between GPL and Artistic
               g   - GPL: GNU General Public License
               l   - LGPL: "GNU Lesser General Public License" (previously known as
                     "GNU Library General Public License")
               b   - BSD: The BSD License
               a   - Artistic license alone
               2   - Artistic license 2.0 or later
               o   - open source: appoved by
               d   - allows distribution without restrictions
               r   - restricted distribtion
               n   - no license at all

           Forces CPAN to perform a task that it normally would have refused to do. Force takes as arguments a method
           name to be called and any number of additional arguments that should be passed to the called method.  The
           internals of the object get the needed changes so that does not refuse to take the action. See also
           the section above on the "force" and the "fforce" pragma.

           Runs a get on the distribution associated with this module.

           Returns the filename of the module found in @INC. The first file found is reported just like perl itself
           stops searching @INC when it finds a module.

           Returns the filename of the module found in PERL5LIB or @INC. The first file found is reported. The advan-
           tage of this method over "inst_file" is that modules that have been tested but not yet installed are
           included because PERL5LIB keeps track of tested modules.

           Returns the version number of the installed module in readable format.

           Returns the version number of the available module in readable format.

           Runs an "install" on the distribution associated with this module.

           Changes to the directory where the distribution associated with this module has been unpacked and opens a
           subshell there. Exiting the subshell returns.

           Runs a "make" on the distribution associated with this module.

           If module is installed, peeks into the module's manpage, reads the headline and returns it. Moreover, if
           the module has been downloaded within this session, does the equivalent on the downloaded module even if it
           is not installed.

           Runs a "perldoc" on this module.

           Runs a "readme" on the distribution associated with this module.

           Calls the reports() method on the associated distribution object.

           Runs a "test" on the distribution associated with this module.

           Returns 1 if the module is installed and up-to-date.

           Returns the author's ID of the module.

       Cache Manager

       Currently the cache manager only keeps track of the build directory ($CPAN::Config->{build_dir}). It is a sim-
       ple FIFO mechanism that deletes complete directories below "build_dir" as soon as the size of all directories
       there gets bigger than $CPAN::Config->{build_cache} (in MB). The contents of this cache may be used for later
       re-installations that you intend to do manually, but will never be trusted by CPAN itself. This is due to the
       fact that the user might use these directories for building modules on different architectures.

       There is another directory ($CPAN::Config->{keep_source_where}) where the original distribution files are kept.
       This directory is not covered by the cache manager and must be controlled by the user. If you choose to have
       the same directory as build_dir and as keep_source_where directory, then your sources will be deleted with the
       same fifo mechanism.


       A bundle is just a perl module in the namespace Bundle:: that does not define any functions or methods. It usu-
       ally only contains documentation.

       It starts like a perl module with a package declaration and a $VERSION variable. After that the pod section
       looks like any other pod with the only difference being that one special pod section exists starting with (ver-

           =head1 CONTENTS

       In this pod section each line obeys the format

               Module_Name [Version_String] [- optional text]

       The only required part is the first field, the name of a module (e.g. Foo::Bar, ie. not the name of the distri-
       bution file). The rest of the line is optional. The comment part is delimited by a dash just as in the man page

       The distribution of a bundle should follow the same convention as other distributions.

       Bundles are treated specially in the CPAN package. If you say 'install Bundle::Tkkit' (assuming such a bundle
       exists), CPAN will install all the modules in the CONTENTS section of the pod. You can install your own Bundles
       locally by placing a conformant Bundle file somewhere into your @INC path. The autobundle() command which is
       available in the shell interface does that for you by including all currently installed modules in a snapshot
       bundle file.

       If you have a local mirror of CPAN and can access all files with "file:" URLs, then you only need a perl better
       than perl5.003 to run this module. Otherwise Net::FTP is strongly recommended. LWP may be required for non-UNIX
       systems or if your nearest CPAN site is associated with a URL that is not "ftp:".

       If you have neither Net::FTP nor LWP, there is a fallback mechanism implemented for an external ftp command or
       for an external lynx command.

       Finding packages and VERSION

       This module presumes that all packages on CPAN

       ? declare their $VERSION variable in an easy to parse manner. This prerequisite can hardly be relaxed because
         it consumes far too much memory to load all packages into the running program just to determine the $VERSION
         variable. Currently all programs that are dealing with version use something like this

             perl -MExtUtils::MakeMaker -le \
                 'print MM->parse_version(shift)' filename

         If you are author of a package and wonder if your $VERSION can be parsed, please try the above method.

       ? come as compressed or gzipped tarfiles or as zip files and contain a "Makefile.PL" or "Build.PL" (well, we
         try to handle a bit more, but without much enthusiasm).


       The debugging of this module is a bit complex, because we have interferences of the software producing the
       indices on CPAN, of the mirroring process on CPAN, of packaging, of configuration, of synchronicity, and of
       bugs within

       For debugging the code of itself in interactive mode some more or less useful debugging aid can be
       turned on for most packages within with one of

       o debug package...
         sets debug mode for packages.

       o debug -package...
         unsets debug mode for packages.

       o debug all
         turns debugging on for all packages.

       o debug number

       which sets the debugging packages directly. Note that "o debug 0" turns debugging off.

       What seems quite a successful strategy is the combination of "reload cpan" and the debugging switches. Add a
       new debug statement while running in the shell and then issue a "reload cpan" and see the new debugging mes-
       sages immediately without losing the current context.

       "o debug" without an argument lists the valid package names and the current set of packages in debugging mode.
       "o debug" has built-in completion support.

       For debugging of CPAN data there is the "dump" command which takes the same arguments as make/test/install and
       outputs each object's Data::Dumper dump. If an argument looks like a perl variable and contains one of "$", "@"
       or "%", it is eval()ed and fed to Data::Dumper directly.

       Floppy, Zip, Offline Mode works nicely without network too. If you maintain machines that are not networked at all, you should
       consider working with file: URLs. Of course, you have to collect your modules somewhere first. So you might use to put together all you need on a networked machine. Then copy the $CPAN::Config->{keep_source_where}
       (but not $CPAN::Config->{build_dir}) directory on a floppy. This floppy is kind of a personal CPAN. on
       the non-networked machines works nicely with this floppy. See also below the paragraph about CD-ROM support.

       Basic Utilities for Programmers

         Returns true if the module is installed. Used to load all modules into the running which are consid-
         ered optional. The config variable "dontload_list" can be used to intercept the "has_inst()" call such that
         an optional module is not loaded despite being available. For example the following command will prevent that
         "" is being loaded:

             cpan> o conf dontload_list push YAML

         See the source for details.

         Returns true if the module is installed and is in a usable state. Only useful for a handful of modules that
         are used internally. See the source for details.

         The constructor for all the singletons used to represent modules, distributions, authors and bundles. If the
         object already exists, this method returns the object, otherwise it calls the constructor.

       There's no strong security layer in helps you to install foreign, unmasked, unsigned code on
       your machine. We compare to a checksum that comes from the net just as the distribution file itself. But we try
       to make it easy to add security on demand:

       Cryptographically signed modules

       Since release 1.77 has been able to verify cryptographically signed module distributions using Mod-
       ule::Signature.  The CPAN modules can be signed by their authors, thus giving more security.  The simple
       unsigned MD5 checksums that were used before by CPAN protect mainly against accidental file corruption.

       You will need to have Module::Signature installed, which in turn requires that you have at least one of
       Crypt::OpenPGP module or the command-line gpg tool installed.

       You will also need to be able to connect over the Internet to the public keyservers, like, and
       their port 11731 (the HKP protocol).

       The configuration parameter check_sigs is there to turn signature checking on or off.

       Most functions in package CPAN are exported per default. The reason for this is that the primary use is
       intended for the cpan shell or for one-liners.

       When the CPAN shell enters a subshell via the look command, it sets the environment CPAN_SHELL_LEVEL to 1 or
       increments it if it is already set.

       When CPAN runs, it sets the environment variable PERL5_CPAN_IS_RUNNING to the ID of the running process. It
       also sets PERL5_CPANPLUS_IS_RUNNING to prevent runaway processes which could happen with older versions of Mod-

       When running "perl Makefile.PL", the environment variable "PERL5_CPAN_IS_EXECUTING" is set to the full path of
       the "Makefile.PL" that is being executed. This prevents runaway processes with newer versions of Mod-

       When the config variable ftp_passive is set, all downloads will be run with the environment variable FTP_PAS-
       SIVE set to this value. This is in general a good idea as it influences both Net::FTP and LWP based connec-
       tions. The same effect can be achieved by starting the cpan shell with this environment variable set. For
       Net::FTP alone, one can also always set passive mode by running libnetcfg.

       Populating a freshly installed perl with my favorite modules is pretty easy if you maintain a private bundle
       definition file. To get a useful blueprint of a bundle definition file, the command autobundle can be used on
       the CPAN shell command line. This command writes a bundle definition file for all modules that are installed
       for the currently running perl interpreter. It's recommended to run this command only once and from then on
       maintain the file manually under a private name, say Bundle/ With a clever bundle file you can
       then simply say

           cpan> install Bundle::my_bundle

       then answer a few questions and then go out for a coffee.

       Maintaining a bundle definition file means keeping track of two things: dependencies and interactivity.
       sometimes fails on calculating dependencies because not all modules define all MakeMaker attributes correctly,
       so a bundle definition file should specify prerequisites as early as possible. On the other hand, it's a bit
       annoying that many distributions need some interactive configuring. So what I try to accomplish in my private
       bundle file is to have the packages that need to be configured early in the file and the gentle ones later, so
       I can go out after a few minutes and leave untended.

       Thanks to Graham Barr for contributing the following paragraphs about the interaction between perl, and various
       firewall configurations. For further information on firewalls, it is recommended to consult the documentation
       that comes with the ncftp program. If you are unable to go through the firewall with a simple Perl setup, it is
       very likely that you can configure ncftp so that it works for your firewall.

       Three basic types of firewalls

       Firewalls can be categorized into three basic types.

       http firewall
           This is where the firewall machine runs a web server and to access the outside world you must do it via the
           web server. If you set environment variables like http_proxy or ftp_proxy to a values beginning with
           http:// or in your web browser you have to set proxy information then you know you are running an http

           To access servers outside these types of firewalls with perl (even for ftp) you will need to use LWP.

       ftp firewall
           This where the firewall machine runs an ftp server. This kind of firewall will only let you access ftp
           servers outside the firewall.  This is usually done by connecting to the firewall with ftp, then entering a
           username like ""

           To access servers outside these type of firewalls with perl you will need to use Net::FTP.

       One way visibility
           I say one way visibility as these firewalls try to make themselves look invisible to the users inside the
           firewall. An FTP data connection is normally created by sending the remote server your IP address and then
           listening for the connection. But the remote server will not be able to connect to you because of the fire-
           wall. So for these types of firewall FTP connections need to be done in a passive mode.

           There are two that I can think off.

               If you are using a SOCKS firewall you will need to compile perl and link it with the SOCKS library,
               this is what is normally called a 'socksified' perl. With this executable you will be able to connect
               to servers outside the firewall as if it is not there.

           IP Masquerade
               This is the firewall implemented in the Linux kernel, it allows you to hide a complete network behind
               one IP address. With this firewall no special compiling is needed as you can access hosts directly.

               For accessing ftp servers behind such firewalls you usually need to set the environment variable
               "FTP_PASSIVE" or the config variable ftp_passive to a true value.

       Configuring lynx or ncftp for going through a firewall

       If you can go through your firewall with e.g. lynx, presumably with a command such as

           /usr/local/bin/lynx -pscott:tiger

       then you would configure with the command

           o conf lynx "/usr/local/bin/lynx -pscott:tiger"

       That's all. Similarly for ncftp or ftp, you would configure something like

           o conf ncftp "/usr/bin/ncftp -f /home/scott/ncftplogin.cfg"

       Your mileage may vary...

       1)  I installed a new version of module X but CPAN keeps saying, I have the old version installed

           Most probably you do have the old version installed. This can happen if a module installs itself into a
           different directory in the @INC path than it was previously installed. This is not really a prob-
           lem, you would have the same problem when installing the module manually. The easiest way to prevent this
           behaviour is to add the argument "UNINST=1" to the "make install" call, and that is why many people add
           this argument permanently by configuring

             o conf make_install_arg UNINST=1

       2)  So why is UNINST=1 not the default?

           Because there are people who have their precise expectations about who may install where in the @INC path
           and who uses which @INC array. In fine tuned environments "UNINST=1" can cause damage.

       3)  I want to clean up my mess, and install a new perl along with all modules I have. How do I go about it?

           Run the autobundle command for your old perl and optionally rename the resulting bundle file (e.g. Bun-
           dle/, install the new perl with the Configure option prefix, e.g.

               ./Configure -Dprefix=/usr/local/perl-

           Install the bundle file you produced in the first step with something like

               cpan> install Bundle::mybundle

           and you're done.

       4)  When I install bundles or multiple modules with one command there is too much output to keep track of.

           You may want to configure something like

             o conf make_arg "| tee -ai /root/.cpan/logs/make.out"
             o conf make_install_arg "| tee -ai /root/.cpan/logs/make_install.out"

           so that STDOUT is captured in a file for later inspection.

       5)  I am not root, how can I install a module in a personal directory?

           First of all, you will want to use your own configuration, not the one that your root user installed. If
           you do not have permission to write in the cpan directory that root has configured, you will be asked if
           you want to create your own config. Answering "yes" will bring you into CPAN's configuration stage, using
           the system config for all defaults except things that have to do with CPAN's work directory, saving your
           choices to your file.

           You can also manually initiate this process with the following command:

               % perl -MCPAN -e 'mkmyconfig'

           or by running


           from the CPAN shell.

           You will most probably also want to configure something like this:

             o conf makepl_arg "LIB=~/myperl/lib \
                               INSTALLMAN1DIR=~/myperl/man/man1 \
                               INSTALLMAN3DIR=~/myperl/man/man3 \
                               INSTALLSCRIPT=~/myperl/bin \

           and then (oh joy) the equivalent command for Module::Build. That would be

             o conf mbuildpl_arg "--lib=~/myperl/lib \
                               --installman1dir=~/myperl/man/man1 \
                               --installman3dir=~/myperl/man/man3 \
                               --installscript=~/myperl/bin \

           You can make this setting permanent like all "o conf" settings with "o conf commit" or by setting
           "auto_commit" beforehand.

           You will have to add ~/myperl/man to the MANPATH environment variable and also tell your perl programs to
           look into ~/myperl/lib, e.g. by including

             use lib "$ENV{HOME}/myperl/lib";

           or setting the PERL5LIB environment variable.

           While we're speaking about $ENV{HOME}, it might be worth mentioning, that for Windows we use the
           File::HomeDir module that provides an equivalent to the concept of the home directory on Unix.

           Another thing you should bear in mind is that the UNINST parameter can be dangerous when you are installing
           into a private area because you might accidentally remove modules that other people depend on that are not
           using the private area.

       6)  How to get a package, unwrap it, and make a change before building it?

           Have a look at the "look" (!) command.

       7)  I installed a Bundle and had a couple of fails. When I retried, everything resolved nicely. Can this be
           fixed to work on first try?

           The reason for this is that CPAN does not know the dependencies of all modules when it starts out. To
           decide about the additional items to install, it just uses data found in the META.yml file or the generated
           Makefile. An undetected missing piece breaks the process. But it may well be that your Bundle installs some
           prerequisite later than some depending item and thus your second try is able to resolve everything.  Please
           note, does not know the dependency tree in advance and cannot sort the queue of things to install
           in a topologically correct order. It resolves perfectly well IF all modules declare the prerequisites cor-
           rectly with the PREREQ_PM attribute to MakeMaker or the "requires" stanza of Module::Build. For bundles
           which fail and you need to install often, it is recommended to sort the Bundle definition file manually.

       8)  In our intranet we have many modules for internal use. How can I integrate these modules with but
           without uploading the modules to CPAN?

           Have a look at the CPAN::Site module.

       9)  When I run CPAN's shell, I get an error message about things in my /etc/inputrc (or ~/.inputrc) file.

           These are readline issues and can only be fixed by studying readline configuration on your architecture and
           adjusting the referenced file accordingly. Please make a backup of the /etc/inputrc or ~/.inputrc and edit
           them. Quite often harmless changes like uppercasing or lowercasing some arguments solves the problem.

       10) Some authors have strange characters in their names.

           Internally uses the UTF-8 charset. If your terminal is expecting ISO-8859-1 charset, a converter
           can be activated by setting term_is_latin to a true value in your config file. One way of doing so would be

               cpan> o conf term_is_latin 1

           If other charset support is needed, please file a bugreport against at and describe
           your needs. Maybe we can extend the support or maybe UTF-8 terminals become widely available.

           Note: this config variable is deprecated and will be removed in a future version of It will be
           replaced with the conventions around the family of $LANG and $LC_* environment variables.

       11) When an install fails for some reason and then I correct the error condition and retry, refuses to
           install the module, saying "Already tried without success".

           Use the force pragma like so

             force install Foo::Bar

           Or you can use

             look Foo::Bar

           and then 'make install' directly in the subshell.

       12) How do I install a "DEVELOPER RELEASE" of a module?

           By default, CPAN will install the latest non-developer release of a module. If you want to install a dev
           release, you have to specify the partial path starting with the author id to the tarball you wish to
           install, like so:

               cpan> install KWILLIAMS/Module-Build-0.27_07.tar.gz

           Note that you can use the "ls" command to get this path listed.

       13) How do I install a module and all its dependencies from the commandline, without being prompted for any-
           thing, despite my CPAN configuration (or lack thereof)?

           CPAN uses ExtUtils::MakeMaker's prompt() function to ask its questions, so if you set the
           PERL_MM_USE_DEFAULT environment variable, you shouldn't be asked any questions at all (assuming the modules
           you are installing are nice about obeying that variable as well):

               % PERL_MM_USE_DEFAULT=1 perl -MCPAN -e 'install My::Module'

       14) How do I create a Module::Build based Build.PL derived from an ExtUtils::MakeMaker focused Makefile.PL?



       15) I'm frequently irritated with the CPAN shell's inability to help me select a good mirror.

           The urllist config parameter is yours. You can add and remove sites at will. You should find out which
           sites have the best uptodateness, bandwidth, reliability, etc. and are topologically close to you. Some
           people prefer fast downloads, others uptodateness, others reliability.  You decide which to try in which

           Henk P. Penning maintains a site that collects data about CPAN sites:


           Also, feel free to play with experimental features. Run

             o conf init randomize_urllist ftpstats_period ftpstats_size

           and choose your favorite parameters. After a few downloads running the "hosts" command will probably assist
           you in choosing the best mirror sites.

       16) Why do I get asked the same questions every time I start the shell?

           You can make your configuration changes permanent by calling the command "o conf commit". Alternatively set
           the "auto_commit" variable to true by running "o conf init auto_commit" and answering the following ques-
           tion with yes.

       17) Older versions of had the original root directory of all tarballs in the build directory. Now there
           are always random characters appended to these directory names. Why was this done?

           The random characters are provided by File::Temp and ensure that each module's individual build directory
           is unique. This makes running in concurrent processes simultaneously safe.

       18) Speaking of the build directory. Do I have to clean it up myself?

           You have the choice to set the config variable "scan_cache" to "never". Then you must clean it up yourself.
           The other possible value, "atstart" only cleans up the build directory when you start the CPAN shell. If
           you never start up the CPAN shell, you probably also have to clean up the build directory yourself.

       OLD PERL VERSIONS is regularly tested to run under 5.004, 5.005, and assorted newer versions. It is getting more and more
       difficult to get the minimal prerequisites working on older perls. It is close to impossible to get the whole
       Bundle::CPAN working there. If you're in the position to have only these old versions, be advised that CPAN is
       designed to work fine without the Bundle::CPAN installed.

       To get things going, note that GBARR/Scalar-List-Utils-1.18.tar.gz is compatible with ancient perls and that
       File::Temp is listed as a prerequisite but CPAN has reasonable workarounds if it is missing.


       This module and its competitor, the CPANPLUS module, are both much cooler than the other. is older.
       CPANPLUS was designed to be more modular but it was never tried to make it compatible with

       This software enables you to upgrade software on your computer and so is inherently dangerous because the newly
       installed software may contain bugs and may alter the way your computer works or even make it unusable. Please
       consider backing up your data before every upgrade.

       Please report bugs via <>;

       Before submitting a bug, please make sure that the traditional method of building a Perl module package from a
       shell by following the installation instructions of that package still works in your environment.

       Andreas Koenig "<>"

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

       See <>;

       Kawai,Takanori provides a Japanese translation of this manpage at <http://home->

       cpan, CPAN::Nox, CPAN::Version

perl v5.8.8                       2008-10-13                           CPAN(3)