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

    Interactive mode:

      perl -MCPAN -e shell;

    Batch mode:

      use CPAN;

      autobundle, clean, install, make, recompile, test

    This module will eventually be replaced by CPANPLUS. CPANPLUS is kind of
    a modern rewrite from ground up with greater extensibility and more
    features but no full compatibility. If you're new to, you
    probably should investigate if CPANPLUS is the better choice for you. If
    you're already used to you're welcome to continue using it, if
    you accept that its development is mostly (though not completely)

    The CPAN module is designed to automate the make and install of perl
    modules and extensions. It includes some primitive searching
    capabilities and knows how to use Net::FTP or LWP (or lynx or an
    external ftp client) to fetch the raw data from the net.

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

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

    The package contains a session manager and a cache manager. There is no
    status retained between sessions. The session manager keeps track of
    what has been fetched, built and installed in the current session. The
    cache manager keeps track of the disk space occupied by the make
    processes and deletes excess space according to a simple FIFO mechanism.

    For extended searching capabilities there's a plugin for CPAN available,
    "CPAN::WAIT". "CPAN::WAIT" is a full-text search engine that indexes all
    documents available in CPAN authors directories. If "CPAN::WAIT" is
    installed on your system, the interactive shell of will enable
    the "wq", "wr", "wd", "wl", and "wh" commands which send queries to the
    WAIT server that has been configured for your installation.

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

  Interactive Mode
    The interactive mode is entered by running

        perl -MCPAN -e shell

    which puts you into a readline interface. You will have the most fun if
    you install Term::ReadKey and Term::ReadLine to enjoy both history and
    command completion.

    Once you are on the command line, type 'h' and the rest should be

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

    The most common uses of the interactive modes are

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

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

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

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

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

        install <distribution_file>

      also is run unconditionally. But for

        install <module>

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

      CPAN also keeps track of what it has done within the current session
      and doesn't try to build a package a second time regardless if it
      succeeded or not. The "force" pragma may precede another command
      (currently: "make", "test", or "install") and executes the command
      from scratch.


          cpan> install OpenGL
          OpenGL is up to date.
          cpan> force install OpenGL
          Running make

      The "notest" pragma may be set to skip the test part in the build


          cpan> notest install Tk

      A "clean" command results in a

        make clean

      being executed within the distribution file's working directory.

    get, readme, perldoc, look module or distribution
      "get" downloads a distribution file without further action. "readme"
      displays the README file of the associated distribution. "Look" gets
      and untars (if not yet done) the distribution file, changes to the
      appropriate directory and opens a subshell process in that directory.
      "perldoc" displays the pod documentation of the module in html or
      plain text format.

    ls author
    ls globbing_expresion
      The first form lists all distribution files in and below an author's
      CPAN directory as they are stored in the CHECKUMS files distrbute on

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

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

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

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

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

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

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

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

  The four "CPAN::*" Classes: Author, Bundle, Module, Distribution
    Although it may be considered internal, the class hierarchy does matter
    for both users and programmer. deals with above mentioned four
    classes, and all those classes share a set of methods. A classical
    single 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

             Namespace                         Class

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

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

        install Foo

    This would install the complete distribution file (say
    BAR/Foo-1.23.tar.gz) with all accompanying material. But if you would
    like to install version 1.23_90, you need to know where the distribution
    file resides on CPAN 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.

  Programmer's interface
    If you do not enter the shell, the available shell commands are both
    available as methods ("CPAN::Shell->install(...)") and as functions in
    the calling package ("install(...)").

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

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

      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 fro distributions.

    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)){
              my $obj = CPAN::Shell->expand('Module',$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 write a cronjob to watch The CPAN, you could list
      all modules that need updating. First a quick and dirty way:

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

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

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

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

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

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

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

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

  Methods in the other Classes
    The programming interface for the classes CPAN::Module,
    CPAN::Distribution, CPAN::Bundle, and CPAN::Author is still considered
    beta and partially even alpha. In the following paragraphs only those
    methods are documented that have proven useful over a longer time and
    thus are unlikely to change.

        Returns a one-line description of the author

        Returns a multi-line description of the author

        Returns the author's email address

        Returns the author's name

        An alias for fullname

        Returns a one-line description of the bundle

        Returns a multi-line description of the bundle

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

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

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

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

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

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

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

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

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

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

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

        Returns a one-line description of the distribution

        Returns a multi-line description of the distribution

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

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

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

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


        Returns the directory into which this distribution has been

        Forces CPAN to perform a task that normally would have failed. Force
        takes as arguments a method name to be called and any number of
        additional arguments that should be passed to the called method. The
        internals of the object get the needed changes so that does
        not refuse to take the action.

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

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

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

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

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

        Returns the hash reference that has been announced by a distribution
        as the "requires" element of the META.yml or the "PREREQ_PM" hash in
        the "Makefile.PL". Note: works only after an attempt has been made
        to "make" the distribution. Returns undef otherwise.

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

        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 external command
        html2text and runs it through the pager specified in

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

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

        Forces a reload of all indices.

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

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

        Returns a one-line description of the module

        Returns a multi-line description of the module

        Runs a clean on the distribution associated with this module.

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

        Returns the latest version of this module available on CPAN.

        Runs a cvs_import on the distribution associated with this module.

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

        Forces CPAN to perform a task that normally would have failed. Force
        takes as arguments a method name to be called and any number of
        additional arguments that should be passed to the called method. The
        internals of the object get the needed changes so that does
        not refuse to take the action.

        Runs a get on the distribution associated with this module.

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

        Returns the version number of the module in readable format.

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

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

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

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

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

        Runs a "perldoc" on this module.

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

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

        Returns the author's ID of the module.

  Cache Manager
    Currently the cache manager only keeps track of the build directory
    ($CPAN::Config->{build_dir}). It is a 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

    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, ie. *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

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

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

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

  Finding packages and VERSION
    This module presumes that all packages on CPAN

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

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

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

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

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

    For code debugging in interactive mode you can try "o debug" which will
    list options for debugging the various parts of the code. You should
    know that "o debug" has built-in completion support.

    For data debugging there is the "dump" command which takes the same
    arguments as make/test/install and outputs the object's Data::Dumper

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

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

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

    The configuration dialog can be started any time later again by issuing
    the command " o conf init " in the CPAN shell.

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

      build_cache        size of cache for directories to build modules
      build_dir          locally accessible directory to build modules
      index_expire       after this many days refetch index files
      cache_metadata     use serializer to cache metadata
      cpan_home          local directory reserved for this package
      dontload_hash      anonymous hash: modules in the keys will not be
                         loaded by the CPAN::has_inst() routine
      gzip               location of external program gzip
      histfile           file to maintain history between sessions
      histsize           maximum number of lines to keep in histfile
      inactivity_timeout breaks interactive Makefile.PLs or Build.PLs
                         after this many seconds inactivity. Set to 0 to
                         never break.
                         if true, does not print the startup message
      keep_source_where  directory in which to keep the source (if we do)
      make               location of external make program
      make_arg           arguments that should always be passed to 'make'
                         the make command for running 'make install', for
                         example 'sudo make'
      make_install_arg   same as make_arg for 'make install'
      makepl_arg         arguments passed to 'perl Makefile.PL'
      mbuild_arg         arguments passed to './Build'
      mbuild_install_arg arguments passed to './Build install'
                         command to use instead of './Build' when we are
                         in the install stage, for example 'sudo ./Build'
      mbuildpl_arg       arguments passed to 'perl Build.PL'
      pager              location of external program more (or any pager)
      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)
                         what to do if you are missing module prerequisites
                         ('follow' automatically, 'ask' me, or 'ignore')
      proxy_user         username for accessing an authenticating proxy
      proxy_pass         password for accessing an authenticating proxy
      scan_cache         controls scanning of cache ('atstart' or 'never')
      tar                location of external program tar
      term_is_latin      if true internal UTF-8 is translated to ISO-8859-1
                         (and nonsense for characters outside latin range)
      unzip              location of external program unzip
      urllist            arrayref to nearby CPAN sites (or equivalent locations)
      wait_list          arrayref to a wait server to try (See CPAN::WAIT)
      ftp_proxy,      }  the three usual variables for configuring
        http_proxy,   }  proxy requests. Both as CPAN::Config variables
        no_proxy      }  and as environment variables configurable.

    You can set and query each of these options interactively in the cpan
    shell with the command set defined within the "o conf" command:

    "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

    "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.

  Note on urllist parameter's format
    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:




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

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

    Another peculiarity of urllist is that the site that we could
    successfully fetch the last file from 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.

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

  Cryptographically signed modules
    Since release 1.77 has been able to verify cryptographically
    signed module distributions using 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
    keyservers, like, and their port 11731 (the HKP protocol).

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

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

        cpan> install Bundle::my_bundle

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

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

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

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

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

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

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

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

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

        There are two that I can think off.

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

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

            For accessing ftp servers behind such firewalls you may need to
            set the environment variable "FTP_PASSIVE" to a true value, e.g.

                env FTP_PASSIVE=1 perl -MCPAN -eshell


                perl -MCPAN -e '$ENV{FTP_PASSIVE} = 1; shell'

  Configuring lynx or ncftp for going through a firewall
    If you can go through your firewall with e.g. lynx, presumably with a
    command such as

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

    then you would configure with the command

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

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

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

    Your mileage may vary...

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

        Most probably you do have the old version installed. This can happen
        if a module installs itself into a different directory in the @INC
        path than it was previously installed. This is not really a
        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/, install the new
        perl with the Configure option prefix, e.g.

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

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

            cpan> install Bundle::mybundle

        and you're done.

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

        You may want to configure something like

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

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

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

        First of all, you will want to use your own configuration, not the
        one that your root user installed. The following command sequence is
        a possible approach:

            % mkdir -p $HOME/.cpan/CPAN
            % echo '$CPAN::Config={ };' > $HOME/.cpan/CPAN/
            % cpan
            [...answer all questions...]

        You will most probably like something like this:

          o conf makepl_arg "LIB=~/myperl/lib \
                            INSTALLMAN1DIR=~/myperl/man/man1 \

        You can make this setting permanent like all "o conf" settings with
        "o conf commit".

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

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

        or setting the PERL5LIB environment variable.

        Another thing you should bear in mind is that the UNINST parameter
        should never be set if you are not root.

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

          look Sybase::Sybperl

    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 generated Makefile. An
        undetected missing piece breaks the process. But it may well be that
        your Bundle installs some prerequisite later than some depending
        item and thus your second try is able to resolve everything. Please
        note, does not know the dependency tree in advance and
        cannot sort the queue of things to install in a topologically
        correct order. It resolves perfectly well IFF all modules declare
        the prerequisites correctly with the PREREQ_PM attribute to
        MakeMaker. For bundles which fail and you need to install often, it
        is recommended to sort the Bundle definition file manually. It is
        planned to improve the metadata situation for dependencies on CPAN
        in general, but this will still take some time.

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

        Have a look at the CPAN::Site module.

    9)  When I run CPAN's shell, I get error msg about line 1 to 4, setting
        meta input/output via the /etc/inputrc file.

        Some versions of readline are picky about capitalization in the
        /etc/inputrc file and specifically RedHat 6.2 comes with a
        /etc/inputrc that contains the word "on" in lowercase. Change the
        occurrences of "on" to "On" and the bug should disappear.

    10) Some authors have strange characters in their names.

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

            cpan> ! $CPAN::Config->{term_is_latin}=1

        Extended support for converters will be made available as soon as
        perl becomes stable with regard to charset issues.

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

        Use the force pragma like so

          force install Foo::Bar

        This does a bit more than really needed because it untars the
        distribution again and runs make and test and only then install.

        Or, if you find this is too fast and you would prefer to do smaller
        steps, say

          force get Foo::Bar

        first and then continue as always. "Force get" *forgets* previous
        error conditions.

        Or you can use

          look Foo::Bar

        and then 'make install' directly in the subshell.

        Or you leave the CPAN shell and start it again.

        For the really curious, by accessing internals directly, you *could*

          ! delete  CPAN::Shell->expand("Distribution", \
            CPAN::Shell->expand("Module","Foo::Bar") \

        but this is neither guaranteed to work in the future nor is it a
        decent command.

    If a Makefile.PL requires special customization of libraries, prompts
    the user for special input, etc. then you may find CPAN is not able to
    build the distribution. In that case it is recommended to attempt the
    traditional method of building a Perl module package from a shell, for
    example by using the 'look' command to open a subshell in the
    distribution's own directory.

    Andreas Koenig "<>"

    Kawai,Takanori provides a Japanese translation of this manpage at

    cpan(1), CPAN::Nox(3pm), CPAN::Version(3pm)

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