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

SYNOPSIS
    Interactive mode:

      perl -MCPAN -e shell

    --or--

      cpan

    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

      CPAN::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

DESCRIPTION
    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 LWP, HTTP::Tiny, Net::FTP and certain
    external download clients to fetch distributions from the net.

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

    The CPAN module also supports named and versioned *bundles* of modules.
    Bundles simplify handling 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 using 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
    Enter interactive mode by running

        perl -MCPAN -e shell

    or

        cpan

    which puts you into a readline interface. If "Term::ReadKey" and either
    of "Term::ReadLine::Perl" or "Term::ReadLine::Gnu" are installed,
    history and command completion are supported.

    Once at the command line, type "h" for one-page help screen; the rest
    should be self-explanatory.

    The function call "shell" takes two optional arguments: one the prompt,
    the second 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 to these commands are either strings exactly matching the
      identification string of an object, or regular expressions matched
      case-insensitively against various attributes of the objects. The
      parser only recognizes a regular expression when you enclose it with
      slashes.

      The principle is that the number of objects found 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 more than
      one is found, each object is displayed with the terse method
      "as_glimpse".

      Examples:

        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/MetaSyntactic.pm
            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. Argument processing is as follows:

        known module name in format Foo/Bar.pm   module
        other embedded slash                     distribution
          - with trailing slash dot              directory
        enclosing slashes                        regexp
        known module name in format Foo::Bar     module

      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"). If an argument is enclosed in
      slashes it is treated as a regular expression: it is expanded and if
      the result is a single object (distribution, bundle or module), this
      object is processed.

      Example:

          install Dummy::Perl                   # installs the module
          install AUXXX/Dummy-Perl-3.14.tar.gz  # installs that distribution
          install /Dummy-Perl-3.14/             # same if the regexp is unambiguous

      "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" is run unconditionally. An

        install <distribution_file>

      is also run unconditionally. But for

        install <module>

      CPAN checks whether an install is needed and prints *module up to
      date* if the distribution file containing the module doesn't need
      updating.

      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 of whether
      it succeeded or not. It does not repeat a test run if the test has
      been run successfully before. Same for install runs.

      The "force" pragma may precede another command (currently: "get",
      "make", "test", or "install") to execute the command from scratch and
      attempt to continue past certain errors. See the section below on the
      "force" and the "fforce" pragma.

      The "notest" pragma skips the test part in the build process.

      Example:

          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 module's pod documentation 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 stored in the CHECKSUMS files distributed on CPAN.
      The listing recurses into subdirectories.

      The second form limits or expands 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 that may be changed in some future version.

    "failed"
      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 written to disk after each step. The
      files contain a signature of the currently running perl version for
      later perusal.

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

    The "force" and the "fforce" pragma
      To speed things up in complex installation scenarios, CPAN.pm 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 repeated only if the previous test was unsuccessful. The
      diagnostic message when CPAN.pm refuses to do something 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 corresponding "test" was not successful.

      In all these cases, the user can override this stubborn 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 corresponding 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.

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

      The shell offers to run in *downgraded mode* when another process is
      holding the lockfile. This is an experimental 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
      CPAN.pm 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.

      CPAN.pm ignores SIGPIPE. If the user sets "inactivity_timeout", a
      SIGALRM is used during the run of the "perl Makefile.PL" or "perl
      Build.PL" subprocess. A SIGALRM is also used during module version
      parsing, and is controlled by "version_timeout".

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

  autobundle
    "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. Duplicates of each distribution are suppressed. The name of
    the bundle file is based on the current date and a counter, e.g.
    Bundle/Snapshot_2012_05_21_00.pm. This is installed again by running
    "cpan Bundle::Snapshot_2012_05_21_00", or installing
    "Bundle::Snapshot_2012_05_21_00" from the CPAN shell.

    Return value: path to the written file.

  hosts
    Note: this feature is still in alpha state and may change in future
    versions of CPAN.pm

    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, or if "ftpstats_size" is set to a
    value "<=0", no stats are provided.

  install_tested
    Install all distributions that have been tested successfully but have
    not yet been installed. See also "is_tested".

  is_tested
    List all build directories of distributions that have been tested
    successfully but have not yet been installed. See also "install_tested".

  mkmyconfig
    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.

  r [Module|/Regexp/]...
    scans current perl installation for modules that have a newer version
    available on CPAN and provides a list of them. If called without
    argument, all potential upgrades are listed; if called with arguments
    the list is filtered to the modules and regexps given as arguments.

    The listing looks something like this:

      Package namespace         installed    latest  in CPAN file
      CPAN                        1.94_64    1.9600  ANDK/CPAN-1.9600.tar.gz
      CPAN::Reporter               1.1801    1.1902  DAGOLDEN/CPAN-Reporter-1.1902.tar.gz
      YAML                           0.70      0.73  INGY/YAML-0.73.tar.gz
      YAML::Syck                     1.14      1.17  AVAR/YAML-Syck-1.17.tar.gz
      YAML::Tiny                     1.44      1.50  ADAMK/YAML-Tiny-1.50.tar.gz
      CGI                            3.43      3.55  MARKSTOS/CGI.pm-3.55.tar.gz
      Module::Build::YAML            1.40      1.41  DAGOLDEN/Module-Build-0.3800.tar.gz
      TAP::Parser::Result::YAML      3.22      3.23  ANDYA/Test-Harness-3.23.tar.gz
      YAML::XS                       0.34      0.35  INGY/YAML-LibYAML-0.35.tar.gz

    It suppresses duplicates in the column "in CPAN file" such that
    distributions with many upgradeable modules are listed only once.

    Note that the list is not sorted.

  recent ***EXPERIMENTAL COMMAND***
    The "recent" command downloads a list of recent uploads to CPAN and
    displays them *slowly*. While the command is running, a $SIG{INT} exits
    the loop after displaying 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 CPAN.pm, but the general approach will
    likely remain.

    Note: See also smoke

  recompile
    recompile() is a special command that takes no argument and runs the
    make/test/install cycle with brute force over all installed dynamically
    loadable extensions (a.k.a. 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 reruns the tests and repeats 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 status. 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 CPAN.pm, but the general approach will
    likely remain.

    Note: See also recent

  upgrade [Module|/Regexp/]...
    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. CPAN.pm deals with the four classes
    mentioned above, and those classes all share a set of methods. Classical
    single polymorphism 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 underscore 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, CPAN.pm 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 relative 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 CPAN::Distribution.

  Integrating local directories
    Note: this feature is still in alpha state and may change in future
    versions of CPAN.pm

    Distribution objects are normally distributions from the CPAN, but there
    is a slightly degenerate case for Distribution 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 CPAN.pm 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 without CPAN.pm 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,
    takes care of 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.

  Redirection
    The usual shell redirection symbols " | " and ">" are recognized by the
    cpan shell only when surrounded by whitespace. So piping to pager or
    redirecting output into a file works somewhat as in a normal shell, with
    the stipulation that you must type extra spaces.

  Plugin support ***EXPERIMENTAL***
    Plugins are objects that implement any of currently eight methods:

      pre_get
      post_get
      pre_make
      post_make
      pre_test
      post_test
      pre_install
      post_install

    The "plugin_list" configuration parameter holds a list of strings of the
    form

      Modulename=arg0,arg1,arg2,arg3,...

    eg:

      CPAN::Plugin::Flurb=dir,/opt/pkgs/flurb/raw,verbose,1

    At run time, each listed plugin is instantiated as a singleton object by
    running the equivalent of this pseudo code:

      my $plugin = <string representation from config>;
      <generate Modulename and arguments from $plugin>;
      my $p = $instance{$plugin} ||= Modulename->new($arg0,$arg1,...);

    The generated singletons are kept around from instantiation until the
    end of the shell session. <plugin_list> can be reconfigured at any time
    at run time. While the cpan shell is running, it checks all activated
    plugins at each of the 8 reference points listed above and runs the
    respective method if it is implemented for that object. The method is
    called with the active CPAN::Distribution object passed in as an
    argument.

CONFIGURATION
    When the CPAN module is used for the first time, a configuration
    dialogue 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/Config.pm.

    Default values defined in the CPAN/Config.pm file can be overridden in a
    user specific file: CPAN/MyConfig.pm. Such a file is best placed in
    "$HOME/.cpan/CPAN/MyConfig.pm", because "$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 you.

    If you want to keep your own CPAN/MyConfig.pm somewhere else, you should
    load it before loading CPAN.pm, e.g.:

      perl -I/tmp/somewhere -MCPAN::MyConfig -MCPAN -eshell

      --or--

     perl -I/tmp/somewhere -MCPAN::MyConfig -S cpan

    Once you are in the shell you can change your configuration as follows.

    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 variables.

        Example:

          o conf shell

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

        Example:

          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 ""

        Example:

          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
        corresponding splice command.

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

        Examples:

          o conf urllist unshift http://cpan.dev.local/CPAN
          o conf urllist splice 3 1
          o conf urllist http://cpan1.local http://cpan2.local ftp://ftp.perl.org

    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/Config.pm or CPAN/MyConfig.pm 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
    The following keys in the hash reference $CPAN::Config are currently
    defined:

      allow_installing_module_downgrades
                         allow or disallow installing module downgrades
      allow_installing_outdated_dists
                         allow or disallow installing modules that are
                         indexed in the cpan index pointing to a distro
                         with a higher distro-version number
      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
      build_requires_install_policy
                         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
      cleanup_after_install
                         remove build directory immediately after a
                         successful install and remember that for the
                         duration of the session
      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
      commandnumber_in_prompt
                         boolean if you want to see current command number
      commands_quote     preferred 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
      connect_to_internet_ok
                         whether to 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 environment variable 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
                         disable timeouts.
      index_expire       refetch index files after this many days
      inhibit_startup_message
                         if true, suppress the startup message
      keep_source_where  directory in which to keep the source (if we do)
      load_module_verbosity
                         report loading of optional modules used by CPAN.pm
      lynx               path to external prg
      make               location of external make program
      make_arg           arguments that should always be passed to 'make'
      make_install_make_command
                         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'
      mbuild_install_build_command
                         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
      patches_dir        local directory containing patch files
      perl5lib_verbosity verbosity level for PERL5LIB additions
      plugin_list        list of active hooks (see Plugin support above
                         and the CPAN::Plugin module)
      prefer_external_tar
                         per default all untar operations are done with
                         Archive::Tar; by setting this variable to true
                         the external tar command is used if available
      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 no matter the setting
      prerequisites_policy
                         what to do if you are missing module prerequisites
                         ('follow' automatically, 'ask' me, or 'ignore')
                         For 'follow', also sets PERL_AUTOINSTALL and
                         PERL_EXTUTILS_AUTOINSTALL for "--defaultdeps" if
                         not already set
      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
      pushy_https        use https to cpan.org when possible, otherwise use http
                         to cpan.org and issue a warning
      randomize_urllist  add some randomness to the sequence of the urllist
      recommends_policy  whether recommended prerequisites should be included
      scan_cache         controls scanning of cache ('atstart', 'atexit' or 'never')
      shell              your favorite shell
      show_unparsable_versions
                         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
      suggests_policy    whether suggested prerequisites should be included
      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)
      trust_test_report_history
                         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)
      urllist_ping_external
                         use external ping command when autoselecting mirrors
      urllist_ping_verbose
                         increase verbosity when autoselecting mirrors
      use_prompt_default set PERL_MM_USE_DEFAULT for configure/make/test/install
      use_sqlite         use CPAN::SQLite for metadata storage (fast and lean)
      username           your username if you CPAN server wants one
      version_timeout    stops version parsing after this many seconds.
                         Default is 15 secs. Set to 0 to disable.
      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::DeferredCode
      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.

      Examples:

        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
    CPAN.pm changes the current working directory often and needs to
    determine its own current working directory. By default it uses
    Cwd::cwd, but if for some reason this doesn't work on your system,
    configure alternatives according to the following table:

    cwd Calls Cwd::cwd

    getcwd
        Calls Cwd::getcwd

    fastcwd
        Calls Cwd::fastcwd

    getdcwd
        Calls Cwd::getdcwd

    backtickcwd
        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:

        file://localhost/whatever/ftp/pub/CPAN/

    or

        file:///home/ftp/pub/CPAN/

  The urllist parameter has CD-ROM support
    The "urllist" parameter of the configuration table contains a list of
    URLs used for downloading. If the list contains any "file" URLs, CPAN
    always tries 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

    CPAN.pm 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 to
    see whether 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 automatically 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 YAML.pm (or some other YAML module configured in
    "yaml_module") installed, CPAN.pm 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 that
    "randomize_urllist" be set; this introduces some amount of randomness
    into the URL selection.

  The "requires" and "build_requires" dependency declarations
    Since CPAN.pm 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 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 to "yes", then both modules
    declared as "requires" and those declared as "build_requires" are
    treated alike. By setting to "ask/yes" or "ask/no", CPAN.pm asks the
    user and sets the default accordingly.

  Configuration of the allow_installing_* parameters
    The "allow_installing_*" parameters are evaluated during the "make"
    phase. If set to "yes", they allow the testing and the installation of
    the current distro and otherwise have no effect. If set to "no", they
    may abort the build (preventing testing and installing), depending on
    the contents of the "blib/" directory. The "blib/" directory is the
    directory that holds all the files that would usually be installed in
    the "install" phase.

    "allow_installing_outdated_dists" compares the "blib/" directory with
    the CPAN index. If it finds something there that belongs, according to
    the index, to a different dist, it aborts the current build.

    "allow_installing_module_downgrades" compares the "blib/" directory with
    already installed modules, actually their version numbers, as determined
    by ExtUtils::MakeMaker or equivalent. If a to-be-installed module would
    downgrade an already installed module, the current build is aborted.

    An interesting twist occurs when a distroprefs document demands the
    installation of an outdated dist via goto while
    "allow_installing_outdated_dists" forbids it. Without additional
    provisions, this would let the "allow_installing_outdated_dists" win and
    the distroprefs lose. So the proper arrangement in such a case is to
    write a second distroprefs document for the distro that "goto" points to
    and overrule the "cpanconfig" there. E.g.:

      ---
      match:
        distribution: "^MAUKE/Keyword-Simple-0.04.tar.gz"
      goto: "MAUKE/Keyword-Simple-0.03.tar.gz"
      ---
      match:
        distribution: "^MAUKE/Keyword-Simple-0.03.tar.gz"
      cpanconfig:
        allow_installing_outdated_dists: yes

  Configuration for individual distributions (*Distroprefs*)
    (Note: This feature has been introduced in CPAN.pm 1.8854)

    Distributions on CPAN usually behave according to what we call the CPAN
    mantra. Or since the advent of Module::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 environment, extra arguments, or
    interactively--thus disturbing the installation of large bundles like
    Phalanx100 or modules with many dependencies like Plagger.

    The distroprefs system of "CPAN.pm" 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 "CPAN.pm" configuration variables

    *   specify dependencies the original maintainer forgot

    *   disable the installation of an object altogether

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

  Filenames
    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 "CPAN.pm"
    in the "prefs_dir" config variable. Try "o conf init prefs_dir" in the
    CPAN shell to set and activate the distroprefs system.

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

    Filenames can be picked arbitrarily; "CPAN.pm" 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 current distribution matches the YAML document or not.

  Fallback Data::Dumper and Storable
    If neither your configured "yaml_module" nor YAML.pm is installed,
    CPAN.pm 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 '
            @y=LoadFile(shift);
            nstore(\@y, shift)' somefile.yml somefile.st

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

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

      ---
      comment: "Demo"
      match:
        module: "Dancing::Queen"
        distribution: "^CHACHACHA/Dancing-"
        not_distribution: "\.zip$"
        perl: "/usr/local/cariba-perl/bin/perl"
        perlconfig:
          archname: "freebsd"
          not_cc: "gcc"
        env:
          DANCING_FLOOR: "Shubiduh"
      disabled: 1
      cpanconfig:
        make: gmake
      pl:
        args:
          - "--somearg=specialcase"

        env: {}

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

      make:
        args:
          - all
          - extra-all

        env: {}

        expect: []

        commandline: "echo SKIPPING make"

      test:
        args: []

        env: {}

        expect: []

      install:
        args: []

        env:
          WANT_TO_INSTALL: YES

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

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

      depends:
        configure_requires:
          LWP: 5.8
        build_requires:
          Test::Exception: 0.25
        requires:
          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 "CPAN.pm" configuration variables.

        Supported are: "build_requires_install_policy", "check_sigs",
        "make", "make_install_make_command", "prefer_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 works only for META.yml declaring "dynamic_config=0". Use
        with caution.

    goto [string]
        The canonical name of a delegate distribution to install 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 Instructions*.

    match [hash]
        A hashref with one or more of the keys "distribution", "module",
        "perl", "perlconfig", and "env" that specify whether a document is
        targeted at a specific CPAN distribution or installation. Keys
        prefixed with "not_" negates the corresponding match.

        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 matches.

        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 "Config.pm" module. Keys prefixed with "not_" negates
        the corresponding match.

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

        If more than one restriction of "module", "distribution", etc. is
        specified, the results of the separately computed match values must
        all match. If so, 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 an external patch program. If the value for the "-p"
        parameter is 0 or 1 is determined by reading the patch beforehand.
        The path to each patch is either an absolute path on the local
        filesystem or relative to a patch directory specified in the
        "patches_dir" configuration variable or in the format of a canonical
        distro name. For examples please consult the distroprefs/ directory
        in the CPAN.pm distribution (these examples are not installed by
        default).

        Note: if the "applypatch" program is installed and "CPAN::Config"
        knows about it and a patch is written by the "makepatch" program,
        then "CPAN.pm" lets "applypatch" apply the patch. Both "makepatch"
        and "applypatch" 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

    commandline
        A full commandline to run via "system()". During execution, the
        environment variable PERL is set to $^X (but with an absolute path).
        If "commandline" is specified, "args" is not used.

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

        You must install the "Expect" module to use "eexpect". CPAN.pm does
        not install it for you.

        "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. With "mode=deterministic", the timeout denotes the timeout per
        question; with "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 watches the stream from the
        execution of the external program ("perl Makefile.PL", "perl
        Build.PL", "make", etc.).

        For "mode=deterministic", the CPAN.pm injects the corresponding
        answer as soon as the stream matches the regular expression.

        For "mode=anyorder" CPAN.pm answers 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 will happen
        with a question-answer pair after it has been used. In the default
        case (reuse=0) it is removed from the array, avoiding being used
        again accidentally. 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]
        You must install the "Expect" module to use "expect". CPAN.pm does
        not install it for you.

        "expect: <array>" is a short notation for this "eexpect":

                eexpect:
                        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
    syntactic correctness.

  Example Distroprefs Files
    "CPAN.pm" 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 environment and your needs.
    You have been warned:-)

PROGRAMMER'S INTERFACE
    If you do not enter the shell, shell commands are available both 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.:

      CPAN::HandleConfig->load;
      CPAN::Shell::setup_output;
      CPAN::Index->reload;

    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. The arguments on the commandline are
    passed as arguments to the method.

    So if you take for example the shell command

      notest install A B C

    the actually executed command is

      CPAN::Shell->notest("install","A","B","C");

    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.

    expand($type,@things)
      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 returns only the first element of the list.

    expandany(@things)
      Like expand, but returns objects of the appropriate type, i.e.
      CPAN::Bundle objects for bundles, CPAN::Module 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 $mod (qw(Net::FTP Digest::SHA Data::Dumper)) {
              CPAN::Shell->install($mod);
          }

          # 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 schedule a *cron* job to watch 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 any output should all modules be up to date, 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.

      If you prefer to do it more in a programmerish style in one single
      process, something like this may better suit 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 too much output every day, you may want to watch only
      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
        CPAN::Shell->r;

  Methods in the other Classes
    CPAN::Author::as_glimpse()
        Returns a one-line description of the author

    CPAN::Author::as_string()
        Returns a multi-line description of the author

    CPAN::Author::email()
        Returns the author's email address

    CPAN::Author::fullname()
        Returns the author's name

    CPAN::Author::name()
        An alias for fullname

    CPAN::Bundle::as_glimpse()
        Returns a one-line description of the bundle

    CPAN::Bundle::as_string()
        Returns a multi-line description of the bundle

    CPAN::Bundle::clean()
        Recursively runs the "clean" method on all items contained in the
        bundle.

    CPAN::Bundle::contains()
        Returns a list of objects' IDs contained in a bundle. The associated
        objects may be bundles, modules or distributions.

    CPAN::Bundle::force($method,@args)
        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
        CPAN.pm 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.

    CPAN::Bundle::get()
        Recursively runs the "get" method on all items contained in the
        bundle

    CPAN::Bundle::inst_file()
        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.

    CPAN::Bundle::inst_version()
        Like CPAN::Bundle::inst_file, but returns the $VERSION

    CPAN::Bundle::uptodate()
        Returns 1 if the bundle itself and all its members are up-to-date.

    CPAN::Bundle::install()
        Recursively runs the "install" method on all items contained in the
        bundle

    CPAN::Bundle::make()
        Recursively runs the "make" method on all items contained in the
        bundle

    CPAN::Bundle::readme()
        Recursively runs the "readme" method on all items contained in the
        bundle

    CPAN::Bundle::test()
        Recursively runs the "test" method on all items contained in the
        bundle

    CPAN::Distribution::as_glimpse()
        Returns a one-line description of the distribution

    CPAN::Distribution::as_string()
        Returns a multi-line description of the distribution

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

    CPAN::Distribution::pretty_id()
        Returns a string of the form "AUTHORID/TARBALL", where AUTHORID is
        the author's PAUSE ID and TARBALL is the distribution filename.

    CPAN::Distribution::base_id()
        Returns the distribution filename without any archive suffix. E.g
        "Foo-Bar-0.01"

    CPAN::Distribution::clean()
        Changes to the directory where the distribution has been unpacked
        and runs "make clean" there.

    CPAN::Distribution::containsmods()
        Returns a list of IDs of modules contained in a distribution file.
        Works only for distributions listed in the 02packages.details.txt.gz
        file. This typically means that just most recent version of a
        distribution is covered.

    CPAN::Distribution::cvs_import()
        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

        there.

    CPAN::Distribution::dir()
        Returns the directory into which this distribution has been
        unpacked.

    CPAN::Distribution::force($method,@args)
        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
        CPAN.pm does not refuse to take the action. See also the section
        above on the "force" and the "fforce" pragma.

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

    CPAN::Distribution::install()
        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" is issued in
        any case and if this fails, the install is cancelled. The
        cancellation can be avoided by letting "force" run the "install" for
        you.

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

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

    CPAN::Distribution::isa_perl()
        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.

    CPAN::Distribution::look()
        Changes to the directory where the distribution has been unpacked
        and opens a subshell there. Exiting the subshell returns.

    CPAN::Distribution::make()
        First runs the "get" method to make sure the distribution is
        downloaded and unpacked. Changes to the directory where the
        distribution has been unpacked and runs the external commands "perl
        Makefile.PL" or "perl Build.PL" and "make" there.

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

    CPAN::Distribution::prefs()
        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
        alphabetically, and the canonical distro name (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 contained in a distribution are
        matched against the regular expressions in the
        $root->{match}{module} attribute value. The two match values are
        ANDed together. Each of the two attributes are optional.

    CPAN::Distribution::prereq_pm()
        Returns the hash reference that has been announced by a distribution
        as 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" written 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.

    CPAN::Distribution::readme()
        Downloads the README file associated with a distribution and runs it
        through the pager specified in "$CPAN::Config->{pager}".

    CPAN::Distribution::reports()
        Downloads report data for this distribution from www.cpantesters.org
        and displays a subset of them.

    CPAN::Distribution::read_yaml()
        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.)

    CPAN::Distribution::test()
        Changes to the directory where the distribution has been unpacked
        and runs "make test" there.

    CPAN::Distribution::uptodate()
        Returns 1 if all the modules contained in the distribution are
        up-to-date. Relies on containsmods.

    CPAN::Index::force_reload()
        Forces a reload of all indices.

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

    CPAN::InfoObj::dump()
        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.

    CPAN::Module::as_glimpse()
        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 up-to-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 distribution information.

    CPAN::Module::as_string()
        Returns a multi-line description of the module

    CPAN::Module::clean()
        Runs a clean on the distribution associated with this module.

    CPAN::Module::cpan_file()
        Returns the filename on CPAN that is associated with the module.

    CPAN::Module::cpan_version()
        Returns the latest version of this module available on CPAN.

    CPAN::Module::cvs_import()
        Runs a cvs_import on the distribution associated with this module.

    CPAN::Module::description()
        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)

    CPAN::Module::distribution()
        Returns the CPAN::Distribution object that contains the current
        version of this module.

    CPAN::Module::dslip_status()
        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 pause.perl.org 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 maintenance

          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: approved by www.opensource.org
            d   - allows distribution without restrictions
            r   - restricted distribution
            n   - no license at all

    CPAN::Module::force($method,@args)
        Forces CPAN to perform a task it would normally refuse to do. Force
        takes as arguments a method name to be invoked and any number of
        additional arguments to pass that method. The internals of the
        object get the needed changes so that CPAN.pm does not refuse to
        take the action. See also the section above on the "force" and the
        "fforce" pragma.

    CPAN::Module::get()
        Runs a get on the distribution associated with this module.

    CPAN::Module::inst_file()
        Returns the filename of the module found in @INC. The first file
        found is reported, just as perl itself stops searching @INC once it
        finds a module.

    CPAN::Module::available_file()
        Returns the filename of the module found in PERL5LIB or @INC. The
        first file found is reported. The advantage 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.

    CPAN::Module::inst_version()
        Returns the version number of the installed module in readable
        format.

    CPAN::Module::available_version()
        Returns the version number of the available module in readable
        format.

    CPAN::Module::install()
        Runs an "install" on the distribution associated with this module.

    CPAN::Module::look()
        Changes to the directory where the distribution associated with this
        module has been unpacked and opens a subshell there. Exiting the
        subshell returns.

    CPAN::Module::make()
        Runs a "make" on the distribution associated with this module.

    CPAN::Module::manpage_headline()
        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 hasn't been installed yet.

    CPAN::Module::perldoc()
        Runs a "perldoc" on this module.

    CPAN::Module::readme()
        Runs a "readme" on the distribution associated with this module.

    CPAN::Module::reports()
        Calls the reports() method on the associated distribution object.

    CPAN::Module::test()
        Runs a "test" on the distribution associated with this module.

    CPAN::Module::uptodate()
        Returns 1 if the module is installed and up-to-date.

    CPAN::Module::userid()
        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 simple 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.

  Bundles
    A bundle is just a perl module in the namespace Bundle:: that does not
    define any functions or methods. It usually 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 (verbatim):

        =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, i.e. *not* the name of the distribution file). The rest of the
    line is optional. The comment part is delimited by a dash just as in the
    man page header.

    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.

PREREQUISITES
    The CPAN program is trying to depend on as little as possible so the
    user can use it in hostile environment. It works better the more goodies
    the environment provides. For example if you try in the CPAN shell

      install Bundle::CPAN

    or

      install Bundle::CPANxxl

    you will find the shell more convenient than the bare shell before.

    If you have a local mirror of CPAN and can access all files with "file:"
    URLs, then you only need a perl later 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.

UTILITIES
  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
      with little enthusiasm).

  Debugging
    Debugging this module is more than a bit complex due to interference
    from the software producing the indices on CPAN, the mirroring process
    on CPAN, packaging, configuration, synchronicity, and even (gasp!) due
    to bugs within the CPAN.pm module itself.

    For debugging the code of CPAN.pm itself in interactive mode, some
    debugging aid can be turned on for most packages within CPAN.pm 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 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 messages
    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
    CPAN.pm works nicely without network access, too. If you maintain
    machines that are not networked at all, you should consider working with
    "file:" URLs. You'll have to collect your modules somewhere first. So
    you might use CPAN.pm 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. CPAN.pm on the non-networked machines works nicely
    with this floppy. See also below the paragraph about CD-ROM support.

  Basic Utilities for Programmers
    has_inst($module)
      Returns true if the module is installed. Used to load all modules into
      the running CPAN.pm that are considered optional. The config variable
      "dontload_list" intercepts the "has_inst()" call such that an optional
      module is not loaded despite being available. For example, the
      following command will prevent "YAML.pm" from being loaded:

          cpan> o conf dontload_list push YAML

      See the source for details.

    use_inst($module)
      Similary to has_inst() tries to load optional library but also dies if
      library is not available

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

    instance($module)
      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.

    frontend()
    frontend($new_frontend)
      Getter/setter for frontend object. Method just allows to subclass
      CPAN.pm.

SECURITY
    There's no strong security layer in CPAN.pm. CPAN.pm 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, CPAN.pm has been able to verify cryptographically
    signed module distributions using Module::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
    key servers, like pgp.mit.edu, and their port 11731 (the HKP protocol).

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

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

ENVIRONMENT
    When the CPAN shell enters a subshell via the look command, it sets the
    environment CPAN_SHELL_LEVEL to 1, or increments that variable 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
    Module::Install.

    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 Module::Install.

    When the config variable ftp_passive is set, all downloads will be run
    with the environment variable FTP_PASSIVE set to this value. This is in
    general a good idea as it influences both Net::FTP and LWP based
    connections. 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.

POPULATE AN INSTALLATION WITH LOTS OF MODULES
    Populating a freshly installed perl with one's 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 installed for the current perl
    interpreter. It's recommended to run this command once only, and from
    then on maintain the file manually under a private name, say
    Bundle/my_bundle.pm. With a clever bundle file you can then simply say

        cpan> install Bundle::my_bundle

    then answer a few questions and go out for coffee (possibly even in a
    different city).

    Maintaining a bundle definition file means keeping track of two things:
    dependencies and interactivity. CPAN.pm 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 annoying that so many
    distributions need some interactive configuring. So what you can try to
    accomplish in your private bundle file is to have the packages that need
    to be configured early in the file and the gentle ones later, so you can
    go out for coffee after a few minutes and leave CPAN.pm to churn away
    unattended.

WORKING WITH CPAN.pm BEHIND FIREWALLS
    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 likely that you
    can configure *ncftp* so that it works through your firewall.

  Three basic types of firewalls
    Firewalls can be categorized into three basic types.

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

        To access servers outside these types of firewalls with perl (even
        for ftp), you need LWP or HTTP::Tiny.

    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 "[email protected]".

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

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

        There are two that I can think off.

        SOCKS
            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 were
            not there.

        IP Masquerade
            This is when the firewall implemented in the kernel (via NAT, or
            networking address translation), 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 CPAN.pm 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...

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

        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 CPAN.pm
        problem, 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. Bundle/mybundle.pm), install the new
        perl with the Configure option prefix, e.g.

            ./Configure -Dprefix=/usr/local/perl-5.6.78.9

        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?

        As of CPAN 1.9463, if you do not have permission to write the
        default perl library directories, CPAN's configuration process will
        ask you whether you want to bootstrap <local::lib>, which makes
        keeping a personal perl library directory easy.

        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, CPAN.pm 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 correctly 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 CPAN.pm 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 CPAN.pm 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 bug report against
        CPAN.pm at rt.cpan.org 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 CPAN.pm. 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, CPAN.pm refuses to install the module, saying
        "Already tried without success".

        You could use the force pragma like so

          force install Foo::Bar

        Or, to avoid a force install (which would install even if the tests
        fail), you can force only the test and then install:

          force test Foo::Bar
          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 anything, 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?

        http://search.cpan.org/dist/Module-Build-Convert/

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

        CPAN can now help you select a "good" mirror, based on which ones
        have the lowest 'ping' round-trip times. From the shell, use the
        command 'o conf init urllist' and allow CPAN to automatically select
        mirrors for you.

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

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

          http://mirrors.cpan.org/

        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 question with yes.

    17) Older versions of CPAN.pm 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 CPAN.pm 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
        values, "atstart" and "atexit" clean up the build directory when you
        start (or more precisely, after the first extraction into the build
        directory) or exit the CPAN shell, respectively. If you never start
        up the CPAN shell, you probably also have to clean up the build
        directory yourself.

    19) How can I switch to sudo instead of local::lib?

        The following 5 environment veriables need to be reset to the
        previous values: PATH, PERL5LIB, PERL_LOCAL_LIB_ROOT, PERL_MB_OPT,
        PERL_MM_OPT; and these two CPAN.pm config variables must be
        reconfigured: make_install_make_command and
        mbuild_install_build_command. The five env variables have probably
        been overwritten in your $HOME/.bashrc or some equivalent. You
        either find them there and delete their traces and logout/login or
        you override them temporarily, depending on your exact desire. The
        two cpanpm config variables can be set with:

          o conf init /install_.*_command/

        probably followed by

          o conf commit

    20) How do recommends_policy and suggests_policy work, exactly?

        The terms "recommends" and "suggests" have been standardized in
        https://metacpan.org/pod/CPAN::Meta::Spec

        In CPAN.pm, if you set "recommands_policy" to a true value, that
        means: if you then install a distribution "Foo" that *recommends* a
        module "Bar", both "Foo" and "Bar" will be tested and potentially
        installed.

        Similarly, if you set "suggests_policy" to a true value, it means:
        if you install a distribution "Foo" that *suggests* a module "Bar",
        both "Foo" and "Bar" will be tested and potentially installed.

        In either case, when "Foo" passes its tests and "Bar" does not pass
        its tests, "Foo" will be installed nontheless. But if "Foo" does not
        pass its tests, neither will be installed.

        This also works recursively for all recommends and suggests of the
        module "Bar".

        This has also been illustrated by a cpan tester, who wrote:

        I just tested Starlink-AST-3.03 which recommends Tk::Zinc;
        Tk-Zinc-3.306 fails with
        http://www.cpantesters.org/cpan/report/a2de7c38-810d-11ee-9ad4-e2167
        316189a ; nonetheless Starlink-AST-3.03 succeeds with
        http://www.cpantesters.org/cpan/report/9352e754-810d-11ee-90e9-46117
        316189a

COMPATIBILITY
  OLD PERL VERSIONS
    CPAN.pm is regularly tested to run under 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.

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

  CPANMINUS
    In the year 2010 App::cpanminus was launched as a new approach to a cpan
    shell with a considerably smaller footprint. Very cool stuff.

SECURITY ADVICE
    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.

BUGS
    Please report bugs via <http://rt.cpan.org/>

    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.

AUTHOR
    Andreas Koenig "<[email protected]>"

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

    See <http://www.perl.com/perl/misc/Artistic.html>

TRANSLATIONS
    Kawai,Takanori provides a Japanese translation of a very old version of
    this manpage at <http://homepage3.nifty.com/hippo2000/perltips/CPAN.htm>

SEE ALSO
    Many people enter the CPAN shell by running the cpan utility program
    which is installed in the same directory as perl itself. So if you have
    this directory in your PATH variable (or some equivalent in your
    operating system) then typing "cpan" in a console window will work for
    you as well. Above that the utility provides several commandline
    shortcuts.

    melezhik (Alexey) sent me a link where he published a chef recipe to
    work with CPAN.pm: http://community.opscode.com/cookbooks/cpan.