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CPAN::Meta::Spec(3)                  User Contributed Perl Documentation                 CPAN::Meta::Spec(3)



NAME
       CPAN::Meta::Spec - specification for CPAN distribution metadata

VERSION
       version 2.120921

SYNOPSIS
         my $distmeta = {
           name => 'Module-Build',
           abstract => 'Build and install Perl modules',
           description =>  "Module::Build is a system for "
             . "building, testing, and installing Perl modules. "
             . "It is meant to ... blah blah blah ...",
           version  => '0.36',
           release_status => 'stable',
           author   => [
             'Ken Williams <kwilliams@cpan.org>',
             'Module-Build List <module-build@perl.org>', # additional contact
           ],
           license  => [ 'perl_5' ],
           prereqs => {
             runtime => {
               requires => {
                 'perl'   => '5.006',
                 'ExtUtils::Install' => '0',
                 'File::Basename' => '0',
                 'File::Compare'  => '0',
                 'IO::File'   => '0',
               },
               recommends => {
                 'Archive::Tar' => '1.00',
                 'ExtUtils::Install' => '0.3',
                 'ExtUtils::ParseXS' => '2.02',
               },
             },
             build => {
               requires => {
                 'Test::More' => '0',
               },
             }
           },
           resources => {
             license => ['http://dev.perl.org/licenses/'],
           },
           optional_features => {
             domination => {
               description => 'Take over the world',
               prereqs     => {
                 develop => { requires => { 'Genius::Evil'     => '1.234' } },
                 runtime => { requires => { 'Machine::Weather' => '2.0'   } },
               },
             },
           },
           dynamic_config => 1,
           keywords => [ qw/ toolchain cpan dual-life / ],
           'meta-spec' => {
             version => '2',
             url     => 'http://search.cpan.org/perldoc?CPAN::Meta::Spec',
           },
           generated_by => 'Module::Build version 0.36',
         };

DESCRIPTION
       This document describes version 2 of the CPAN distribution metadata specification, also known as the
       "CPAN Meta Spec".

       Revisions of this specification for typo corrections and prose clarifications may be issued as
       CPAN::Meta::Spec 2.x.  These revisions will never change semantics or add or remove specified
       behavior.

       Distribution metadata describe important properties of Perl distributions. Distribution building
       tools like Module::Build, Module::Install, ExtUtils::MakeMaker or Dist::Zilla should create a
       metadata file in accordance with this specification and include it with the distribution for use by
       automated tools that index, examine, package or install Perl distributions.

TERMINOLOGY
       distribution
           This is the primary object described by the metadata. In the context of this document it usually
           refers to a collection of modules, scripts, and/or documents that are distributed together for
           other developers to use.  Examples of distributions are "Class-Container", "libwww-perl", or
           "DBI".

       module
           This refers to a reusable library of code contained in a single file.  Modules usually contain
           one or more packages and are often referred to by the name of a primary package that can be
           mapped to the file name. For example, one might refer to "File::Spec" instead of File/Spec.pm

       package
           This refers to a namespace declared with the Perl "package" statement.  In Perl, packages often
           have a version number property given by the $VERSION variable in the namespace.

       consumer
           This refers to code that reads a metadata file, deserializes it into a data structure in memory,
           or interprets a data structure of metadata elements.

       producer
           This refers to code that constructs a metadata data structure, serializes into a bytestream
           and/or writes it to disk.

       must, should, may, etc.
           These terms are interpreted as described in IETF RFC 2119.

DATA TYPES
       Fields in the "STRUCTURE" section describe data elements, each of which has an associated data type
       as described herein.  There are four primitive types: Boolean, String, List and Map.  Other types are
       subtypes of primitives and define compound data structures or define constraints on the values of a
       data element.

   Boolean
       A Boolean is used to provide a true or false value.  It must be represented as a defined value.

   String
       A String is data element containing a non-zero length sequence of Unicode characters, such as an
       ordinary Perl scalar that is not a reference.

   List
       A List is an ordered collection of zero or more data elements.  Elements of a List may be of mixed
       types.

       Producers must represent List elements using a data structure which unambiguously indicates that
       multiple values are possible, such as a reference to a Perl array (an "arrayref").

       Consumers expecting a List must consider a String as equivalent to a List of length 1.

   Map
       A Map is an unordered collection of zero or more data elements ("values"), indexed by associated
       String elements ("keys").  The Map's value elements may be of mixed types.

   License String
       A License String is a subtype of String with a restricted set of values.  Valid values are described
       in detail in the description of the "license" field.

   URL
       URL is a subtype of String containing a Uniform Resource Locator or Identifier.  [ This type is
       called URL and not URI for historical reasons. ]

   Version
       A Version is a subtype of String containing a value that describes the version number of packages or
       distributions.  Restrictions on format are described in detail in the "Version Formats" section.

   Version Range
       The Version Range type is a subtype of String.  It describes a range of Versions that may be present
       or installed to fulfill prerequisites.  It is specified in detail in the "Version Ranges" section.

STRUCTURE
       The metadata structure is a data element of type Map.  This section describes valid keys within the
       Map.

       Any keys not described in this specification document (whether top-level or within compound data
       structures described herein) are considered custom keys and must begin with an "x" or "X" and be
       followed by an underscore; i.e. they must match the pattern: "qr{\Ax_}i".  If a custom key refers to
       a compound data structure, subkeys within it do not need an "x_" or "X_" prefix.

       Consumers of metadata may ignore any or all custom keys.  All other keys not described herein are
       invalid and should be ignored by consumers.  Producers must not generate or output invalid keys.

       For each key, an example is provided followed by a description.  The description begins with the
       version of spec in which the key was added or in which the definition was modified, whether the key
       is required or optional and the data type of the corresponding data element.  These items are in
       parentheses, brackets and braces, respectively.

       If a data type is a Map or Map subtype, valid subkeys will be described as well.

       Some fields are marked Deprecated.  These are shown for historical context and must not be produced
       in or consumed from any metadata structure of version 2 or higher.

   REQUIRED FIELDS
       abstract

       Example:

         abstract => 'Build and install Perl modules'

       (Spec 1.2) [required] {String}

       This is a short description of the purpose of the distribution.

       author

       Example:

         author => [ 'Ken Williams <kwilliams@cpan.org>' ]

       (Spec 1.2) [required] {List of one or more Strings}

       This List indicates the person(s) to contact concerning the distribution. The preferred form of the
       contact string is:

         contact-name <email-address>

       This field provides a general contact list independent of other structured fields provided within the
       "resources" field, such as "bugtracker".  The addressee(s) can be contacted for any purpose including
       but not limited to (security) problems with the distribution, questions about the distribution or
       bugs in the distribution.

       A distribution's original author is usually the contact listed within this field.  Co-maintainers,
       successor maintainers or mailing lists devoted to the distribution may also be listed in addition to
       or instead of the original author.

       dynamic_config

       Example:

         dynamic_config => 1

       (Spec 2) [required] {Boolean}

       A boolean flag indicating whether a Build.PL or Makefile.PL (or similar) must be executed to
       determine prerequisites.

       This field should be set to a true value if the distribution performs some dynamic configuration
       (asking questions, sensing the environment, etc.) as part of its configuration.  This field should be
       set to a false value to indicate that prerequisites included in metadata may be considered final and
       valid for static analysis.

       This field explicitly does not indicate whether installation may be safely performed without using a
       Makefile or Build file, as there may be special files to install or custom installation targets (e.g.
       for dual-life modules that exist on CPAN as well as in the Perl core).  This field only defines
       whether prerequisites are complete as given in the metadata.

       generated_by

       Example:

         generated_by => 'Module::Build version 0.36'

       (Spec 1.0) [required] {String}

       This field indicates the tool that was used to create this metadata.  There are no defined semantics
       for this field, but it is traditional to use a string in the form "Generating::Package version 1.23"
       or the author's name, if the file was generated by hand.

       license

       Example:

         license => [ 'perl_5' ]

         license => [ 'apache_2', 'mozilla_1_0' ]

       (Spec 2) [required] {List of one or more License Strings}

       One or more licenses that apply to some or all of the files in the distribution.  If multiple
       licenses are listed, the distribution documentation should be consulted to clarify the interpretation
       of multiple licenses.

       The following list of license strings are valid:

        string          description
        -------------   -----------------------------------------------agpl_3 ----------------------------------------------agpl_3
        agpl_3          GNU Affero General Public License, Version 3
        apache_1_1      Apache Software License, Version 1.1
        apache_2_0      Apache License, Version 2.0
        artistic_1      Artistic License, (Version 1)
        artistic_2      Artistic License, Version 2.0
        bsd             BSD License (three-clause)
        freebsd         FreeBSD License (two-clause)
        gfdl_1_2        GNU Free Documentation License, Version 1.2
        gfdl_1_3        GNU Free Documentation License, Version 1.3
        gpl_1           GNU General Public License, Version 1
        gpl_2           GNU General Public License, Version 2
        gpl_3           GNU General Public License, Version 3
        lgpl_2_1        GNU Lesser General Public License, Version 2.1
        lgpl_3_0        GNU Lesser General Public License, Version 3.0
        mit             MIT (aka X11) License
        mozilla_1_0     Mozilla Public License, Version 1.0
        mozilla_1_1     Mozilla Public License, Version 1.1
        openssl         OpenSSL License
        perl_5          The Perl 5 License (Artistic 1 & GPL 1 or later)
        qpl_1_0         Q Public License, Version 1.0
        ssleay          Original SSLeay License
        sun             Sun Internet Standards Source License (SISSL)
        zlib            zlib License

       The following license strings are also valid and indicate other licensing not described above:

        string          description
        -------------   -----------------------------------------------open_source ----------------------------------------------open_source
        open_source     Other Open Source Initiative (OSI) approved license
        restricted      Requires special permission from copyright holder
        unrestricted    Not an OSI approved license, but not restricted
        unknown         License not provided in metadata

       All other strings are invalid in the license field.

       meta-spec

       Example:

         'meta-spec' => {
           version => '2',
           url     => 'http://search.cpan.org/perldoc?CPAN::Meta::Spec',
         }

       (Spec 1.2) [required] {Map}

       This field indicates the version of the CPAN Meta Spec that should be used to interpret the metadata.
       Consumers must check this key as soon as possible and abort further metadata processing if the meta-spec metaspec
       spec version is not supported by the consumer.

       The following keys are valid, but only "version" is required.

       version
           This subkey gives the integer Version of the CPAN Meta Spec against which the document was
           generated.

       url This is a URL of the metadata specification document corresponding to the given version.  This is
           strictly for human-consumption and should not impact the interpretation of the document.

       name

       Example:

         name => 'Module-Build'

       (Spec 1.0) [required] {String}

       This field is the name of the distribution.  This is often created by taking the "main package" in
       the distribution and changing "::" to "-", but the name may be completely unrelated to the packages
       within the distribution.  C.f. http://search.cpan.org/dist/libwww-perl/
       <http://search.cpan.org/dist/libwww-perl/>.

       release_status

       Example:

         release_status => 'stable'

       (Spec 2) [required] {String}

       This field provides the  release status of this distribution.  If the "version" field contains an
       underscore character, then "release_status" must not be "stable."

       The "release_status" field must have one of the following values:

       stable
           This indicates an ordinary, "final" release that should be indexed by PAUSE or other indexers.

       testing
           This indicates a "beta" release that is substantially complete, but has an elevated risk of bugs
           and requires additional testing.  The distribution should not be installed over a stable release
           without an explicit request or other confirmation from a user.  This release status may also be
           used for "release candidate" versions of a distribution.

       unstable
           This indicates an "alpha" release that is under active development, but has been released for
           early feedback or testing and may be missing features or may have serious bugs.  The distribution
           should not be installed over a stable release without an explicit request or other confirmation
           from a user.

       Consumers may use this field to determine how to index the distribution for CPAN or other
       repositories in addition to or in replacement of heuristics based on version number or file name.

       version

       Example:

         version => '0.36'

       (Spec 1.0) [required] {Version}

       This field gives the version of the distribution to which the metadata structure refers.

   OPTIONAL FIELDS
       description

       Example:

           description =>  "Module::Build is a system for "
             . "building, testing, and installing Perl modules. "
             . "It is meant to ... blah blah blah ...",

       (Spec 2) [optional] {String}

       A longer, more complete description of the purpose or intended use of the distribution than the one
       provided by the "abstract" key.

       keywords

       Example:

         keywords => [ qw/ toolchain cpan dual-life / ]

       (Spec 1.1) [optional] {List of zero or more Strings}

       A List of keywords that describe this distribution.  Keywords must not include whitespace.

       no_index

       Example:

         no_index => {
           file      => [ 'My/Module.pm' ],
           directory => [ 'My/Private' ],
           package   => [ 'My::Module::Secret' ],
           namespace => [ 'My::Module::Sample' ],
         }

       (Spec 1.2) [optional] {Map}

       This Map describes any files, directories, packages, and namespaces that are private to the packaging
       or implementation of the distribution and should be ignored by indexing or search tools.

       Valid subkeys are as follows:

       file
           A List of relative paths to files.  Paths must be specified with unix conventions.

       directory
           A List of relative paths to directories.  Paths must be specified with unix conventions.

           [ Note: previous editions of the spec had "dir" instead of "directory" ]

       package
           A List of package names.

       namespace
           A List of package namespaces, where anything below the namespace must be ignored, but not the
           namespace itself.

           In the example above for "no_index", "My::Module::Sample::Foo" would be ignored, but
           "My::Module::Sample" would not.

       optional_features

       Example:

         optional_features => {
           sqlite => {
             description => 'Provides SQLite support',
             prereqs => {
               runtime => {
                 requires => {
                   'DBD::SQLite' => '1.25'
                 }
               }
             }
           }
         }

       (Spec 2) [optional] {Map}

       This Map describes optional features with incremental prerequisites.  Each key of the
       "optional_features" Map is a String used to identify the feature and each value is a Map with
       additional information about the feature.  Valid subkeys include:

       description
           This is a String describing the feature.  Every optional feature should provide a description

       prereqs
           This entry is required and has the same structure as that of the "prereqs" key.  It provides a
           list of package requirements that must be satisfied for the feature to be supported or enabled.

           There is one crucial restriction:  the prereqs of an optional feature must not include
           "configure" phase prereqs.

       Consumers must not include optional features as prerequisites without explicit instruction from users
       (whether via interactive prompting, a function parameter or a configuration value, etc. ).

       If an optional feature is used by a consumer to add additional prerequisites, the consumer should
       merge the optional feature prerequisites into those given by the "prereqs" key using the same
       semantics.  See "Merging and Resolving Prerequisites" for details on merging prerequisites.

       Suggestion for disuse: Because there is currently no way for a distribution to specify a dependency
       on an optional feature of another dependency, the use of "optional_feature" is discouraged.  Instead,
       create a separate, installable distribution that ensures the desired feature is available.  For
       example, if "Foo::Bar" has a "Baz" feature, release a separate "Foo-Bar-Baz" distribution that
       satisfies requirements for the feature.

       prereqs

       Example:

         prereqs => {
           runtime => {
             requires => {
               'perl'          => '5.006',
               'File::Spec'    => '0.86',
               'JSON'          => '2.16',
             },
             recommends => {
               'JSON::XS'      => '2.26',
             },
             suggests => {
               'Archive::Tar'  => '0',
             },
           },
           build => {
             requires => {
               'Alien::SDL'    => '1.00',
             },
           },
           test => {
             recommends => {
               'Test::Deep'    => '0.10',
             },
           }
         }

       (Spec 2) [optional] {Map}

       This is a Map that describes all the prerequisites of the distribution.  The keys are phases of
       activity, such as "configure", "build", "test" or "runtime".  Values are Maps in which the keys name
       the type of prerequisite relationship such as "requires", "recommends", or "suggests" and the value
       provides a set of prerequisite relations.  The set of relations must be specified as a Map of package
       names to version ranges.

       The full definition for this field is given in the "Prereq Spec" section.

       provides

       Example:

         provides => {
           'Foo::Bar' => {
             file    => 'lib/Foo/Bar.pm',
             version => 0.27_02
           },
           'Foo::Bar::Blah' => {
             file    => 'lib/Foo/Bar/Blah.pm',
           },
           'Foo::Bar::Baz' => {
             file    => 'lib/Foo/Bar/Baz.pm',
             version => 0.3,
           },
         }

       (Spec 1.2) [optional] {Map}

       This describes all packages provided by this distribution.  This information is used by distribution
       and automation mechanisms like PAUSE, CPAN, and search.cpan.org to build indexes saying in which
       distribution various packages can be found.

       The keys of "provides" are package names that can be found within the distribution.  The values are
       Maps with the following valid subkeys:

       file
           This field is required.  The value must contain a Unix-style relative file path from the root of
           the distribution to the module containing the package.

       version
           This field contains a Version String for the package, if one exists.

       resources

       Example:

         resources => {
           license     => [ 'http://dev.perl.org/licenses/' ],
           homepage    => 'http://sourceforge.net/projects/module-build',
           bugtracker  => {
             web    => 'http://rt.cpan.org/Public/Dist/Display.html?Name=CPAN-Meta',
             mailto => 'meta-bugs@example.com',
           },
           repository  => {
             url  => 'git://github.com/dagolden/cpan-meta.git',
             web  => 'http://github.com/dagolden/cpan-meta',
             type => 'git',
           },
           x_twitter   => 'http://twitter.com/cpan_linked/',
         }

       (Spec 2) [optional] {Map}

       This field describes resources related to this distribution.

       Valid subkeys include:

       homepage
           The official home of this project on the web.

       license
           A List of URL's that relate to this distribution's license.  As with the top-level "license"
           field, distribution documentation should be consulted to clarify the interpretation of multiple
           licenses provided here.

       bugtracker
           This entry describes the bug tracking system for this distribution.  It is a Map with the
           following valid keys:

             web    - a URL pointing to a web front-end for the bug tracker
             mailto - an email address to which bugs can be sent

       repository
           This entry describes the source control repository for this distribution.  It is a Map with the
           following valid keys:

             url  - a URL pointing to the repository itself
             web  - a URL pointing to a web front-end for the repository
             type - a lowercase string indicating the VCS used

           Because a url like "http://myrepo.example.com/" is ambiguous as to type, producers should provide
           a "type" whenever a "url" key is given.  The "type" field should be the name of the most common
           program used to work with the repository, e.g. git, svn, cvs, darcs, bzr or hg.

   DEPRECATED FIELDS
       build_requires

       (Deprecated in Spec 2) [optional] {String}

       Replaced by "prereqs"

       configure_requires

       (Deprecated in Spec 2) [optional] {String}

       Replaced by "prereqs"

       conflicts

       (Deprecated in Spec 2) [optional] {String}

       Replaced by "prereqs"

       distribution_type

       (Deprecated in Spec 2) [optional] {String}

       This field indicated 'module' or 'script' but was considered meaningless, since many distributions
       are hybrids of several kinds of things.

       license_uri

       (Deprecated in Spec 1.2) [optional] {URL}

       Replaced by "license" in "resources"

       private

       (Deprecated in Spec 1.2) [optional] {Map}

       This field has been renamed to "no_index".

       recommends

       (Deprecated in Spec 2) [optional] {String}

       Replaced by "prereqs"

       requires

       (Deprecated in Spec 2) [optional] {String}

       Replaced by "prereqs"

VERSION NUMBERS
   Version Formats
       This section defines the Version type, used by several fields in the CPAN Meta Spec.

       Version numbers must be treated as strings, not numbers.  For example, 1.200 must not be serialized
       as 1.2.  Version comparison should be delegated to the Perl version module, version 0.80 or newer.

       Unless otherwise specified, version numbers must appear in one of two formats:

       Decimal versions
           Decimal versions are regular "decimal numbers", with some limitations.  They must be non-negative
           and must begin and end with a digit.  A single underscore may be included, but must be between
           two digits.  They must not use exponential notation ("1.23e-2").

              version => '1.234'       # OK
              version => '1.23_04'     # OK

              version => '1.23_04_05'  # Illegal
              version => '1.'          # Illegal
              version => '.1'          # Illegal

       Dotted-integer versions
           Dotted-integer (also known as dotted-decimal) versions consist of positive integers separated by
           full stop characters (i.e. "dots", "periods" or "decimal points").  This are equivalent in format
           to Perl "v-strings", with some additional restrictions on form.  They must be given in "normal"
           form, which has a leading "v" character and at least three integer components.  To retain a one-to-one oneto-one
           to-one mapping with decimal versions, all components after the first should be restricted to the
           range 0 to 999.  The final component may be separated by an underscore character instead of a
           period.

              version => 'v1.2.3'      # OK
              version => 'v1.2_3'      # OK
              version => 'v1.2.3.4'    # OK
              version => 'v1.2.3_4'    # OK
              version => 'v2009.10.31' # OK

              version => 'v1.2'          # Illegal
              version => '1.2.3'         # Illegal
              version => 'v1.2_3_4'      # Illegal
              version => 'v1.2009.10.31' # Not recommended

   Version Ranges
       Some fields (prereq, optional_features) indicate the particular version(s) of some other module that
       may be required as a prerequisite.  This section details the Version Range type used to provide this
       information.

       The simplest format for a Version Range is just the version number itself, e.g. 2.4.  This means that
       at least version 2.4 must be present.  To indicate that any version of a prerequisite is okay, even
       if the prerequisite doesn't define a version at all, use the version 0.

       Alternatively, a version range may use the operators < (less than), <= (less than or equal), >
       (greater than), >= (greater than or equal), == (equal), and != (not equal).  For example, the
       specification "< 2.0" means that any version of the prerequisite less than 2.0 is suitable.

       For more complicated situations, version specifications may be AND-ed together using commas.  The
       specification ">= 1.2, != 1.5, < 2.0" indicates a version that must be at least 1.2, less than 2.0,
       and not equal to 1.5.

PREREQUISITES
   Prereq Spec
       The "prereqs" key in the top-level metadata and within "optional_features" define the relationship
       between a distribution and other packages.  The prereq spec structure is a hierarchical data
       structure which divides prerequisites into Phases of activity in the installation process and
       Relationships that indicate how prerequisites should be resolved.

       For example, to specify that "Data::Dumper" is "required" during the "test" phase, this entry would
       appear in the distribution metadata:

         prereqs => {
           test => {
             requires => {
               'Data::Dumper' => '2.00'
             }
           }
         }

       Phases

       Requirements for regular use must be listed in the "runtime" phase.  Other requirements should be
       listed in the earliest stage in which they are required and consumers must accumulate and satisfy
       requirements across phases before executing the activity. For example, "build" requirements must also
       be available during the "test" phase.

         before action       requirements that must be met
         ----------------    --------------------------------perl -------------------------------perl
         perl Build.PL       configure
         perl Makefile.PL

         make                configure, runtime, build
         Build

         make test           configure, runtime, build, test
         Build test

       Consumers that install the distribution must ensure that runtime requirements are also installed and
       may install dependencies from other phases.

         after action        requirements that must be met
         ----------------    --------------------------------make -------------------------------make
         make install        runtime
         Build install

       configure
           The configure phase occurs before any dynamic configuration has been attempted.  Libraries
           required by the configure phase must be available for use before the distribution building tool
           has been executed.

       build
           The build phase is when the distribution's source code is compiled (if necessary) and otherwise
           made ready for installation.

       test
           The test phase is when the distribution's automated test suite is run.  Any library that is
           needed only for testing and not for subsequent use should be listed here.

       runtime
           The runtime phase refers not only to when the distribution's contents are installed, but also to
           its continued use.  Any library that is a prerequisite for regular use of this distribution
           should be indicated here.

       develop
           The develop phase's prereqs are libraries needed to work on the distribution's source code as its
           author does.  These tools might be needed to build a release tarball, to run author-only tests,
           or to perform other tasks related to developing new versions of the distribution.

       Relationships

       requires
           These dependencies must be installed for proper completion of the phase.

       recommends
           Recommended dependencies are strongly encouraged and should be satisfied except in resource
           constrained environments.

       suggests
           These dependencies are optional, but are suggested for enhanced operation of the described
           distribution.

       conflicts
           These libraries cannot be installed when the phase is in operation.  This is a very rare
           situation, and the "conflicts" relationship should be used with great caution, or not at all.

   Merging and Resolving Prerequisites
       Whenever metadata consumers merge prerequisites, either from different phases or from
       "optional_features", they should merged in a way which preserves the intended semantics of the
       prerequisite structure.  Generally, this means concatenating the version specifications using commas,
       as described in the "Version Ranges" section.

       Another subtle error that can occur in resolving prerequisites comes from the way that modules in
       prerequisites are indexed to distribution files on CPAN.  When a module is deleted from a
       distribution, prerequisites calling for that module could indicate an older distribution should
       installed, potentially overwriting files from a newer distribution.

       For example, as of Oct 31, 2009, the CPAN index file contained these module-distribution mappings:

         Class::MOP                   0.94  D/DR/DROLSKY/Class-MOP-0.94.tar.gz
         Class::MOP::Class            0.94  D/DR/DROLSKY/Class-MOP-0.94.tar.gz
         Class::MOP::Class::Immutable 0.04  S/ST/STEVAN/Class-MOP-0.36.tar.gz

       Consider the case where "Class::MOP" 0.94 is installed.  If a distribution specified
       "Class::MOP::Class::Immutable" as a prerequisite, it could result in Class-MOP-0.36.tar.gz being
       installed, overwriting any files from Class-MOP-0.94.tar.gz.

       Consumers of metadata should test whether prerequisites would result in installed module files being
       "downgraded" to an older version and may warn users or ignore the prerequisite that would cause such
       a result.

SERIALIZATION
       Distribution metadata should be serialized (as a hashref) as JSON-encoded data and packaged with
       distributions as the file META.json.

       In the past, the distribution metadata structure had been packed with distributions as META.yml, a
       file in the YAML Tiny format (for which, see YAML::Tiny).  Tools that consume distribution metadata
       from disk should be capable of loading META.yml, but should prefer META.json if both are found.

NOTES FOR IMPLEMENTORS
   Extracting Version Numbers from Perl Modules
       To get the version number from a Perl module, consumers should use the "MM->parse_version($file)"
       method provided by ExtUtils::MakeMaker or Module::Metadata.  For example, for the module given by
       $mod, the version may be retrieved in one of the following ways:

         # via ExtUtils::MakeMaker
         my $file = MM->_installed_file_for_module($mod);
         my $version = MM->parse_version($file)

       The private "_installed_file_for_module" method may be replaced with other methods for locating a
       module in @INC.

         # via Module::Metadata
         my $info = Module::Metadata->new_from_module($mod);
         my $version = $info->version;

       If only a filename is available, the following approach may be used:

         # via Module::Build
         my $info = Module::Metadata->new_from_file($file);
         my $version = $info->version;

   Comparing Version Numbers
       The version module provides the most reliable way to compare version numbers in all the various ways
       they might be provided or might exist within modules.  Given two strings containing version numbers,
       $v1 and $v2, they should be converted to "version" objects before using ordinary comparison
       operators.  For example:

         use version;
         if ( version->new($v1) <=> version->new($v2) ) {
           print "Versions are not equal\n";
         }

       If the only comparison needed is whether an installed module is of a sufficiently high version, a
       direct test may be done using the string form of "eval" and the "use" function.  For example, for
       module $mod and version prerequisite $prereq:

         if ( eval "use $mod $prereq (); 1" ) {
           print "Module $mod version is OK.\n";
         }

       If the values of $mod and $prereq have not been scrubbed, however, this presents security
       implications.

SEE ALSO
       CPAN, <http://www.cpan.org/>

       CPAN.pm, <http://search.cpan.org/dist/CPAN/>

       CPANPLUS, <http://search.cpan.org/dist/CPANPLUS/>

       ExtUtils::MakeMaker, http://search.cpan.org/dist/ExtUtils-MakeMaker/
       <http://search.cpan.org/dist/ExtUtils-MakeMaker/>

       Module::Build, http://search.cpan.org/dist/Module-Build/ <http://search.cpan.org/dist/Module-Build/>

       Module::Install, http://search.cpan.org/dist/Module-Install/ <http://search .cpan.org/dist/Module-
       Установка />

       JSON, <http://json.org/>

       YAML, <http://www.yaml.org/>

CONTRIBUTORS
       Ken Williams wrote the original CPAN Meta Spec (also known as the "META.yml spec") in 2003 and
       maintained it through several revisions with input from various members of the community.  In 2005,
       Randy Sims redrafted it from HTML to POD for the version 1.2 release.  Ken continued to maintain the
       spec through version 1.4.

       In late 2009, David Golden organized the version 2 proposal review process.  David and Ricardo Signes
       drafted the final version 2 spec in April 2010 based on the version 1.4 spec and patches contributed
       during the proposal process.

       Several others have contributed patches over the years.  The full list of contributors in the
       repository history currently includes:

         2shortplanks
         Avar Arnfjord Bjarmason
         Christopher J. Madsen
         Damyan Ivanov
         David Golden
         Eric Wilhelm
         Ken Williams
         Lars DIECKOW
         Michael G. Schwern
         Randy Sims
         Ricardo Signes

AUTHORS
       •   David Golden <dagolden@cpan.org>

       •   Ricardo Signes <rjbs@cpan.org>

COPYRIGHT AND LICENSE
       This software is copyright (c) 2010 by David Golden and Ricardo Signes.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.



perl v5.16.2                                     2012-04-01                              CPAN::Meta::Spec(3)