Provided by: perl-doc_5.14.2-6ubuntu2_all bug

NAME

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

VERSION

       version 2.110440

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',
           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          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     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 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 convetions.

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

           [ 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 preqreqs of an optional feature must not
           include "configure" phase prereqs.

       Consumers must not include optional features as prerequisites without explict 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 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://github.com/dagolden/cpan-meta-spec/issues',
             mailto => 'meta-bugs@example.com',
           },
           repository  => {
             url  => 'git://github.com/dagolden/cpan-meta-spec.git',
             web  => 'http://github.com/dagolden/cpan-meta-spec',
             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 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 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 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 the
       Module::Build::ModuleInfo module provided with Module::Build.  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::Build
         my $info = Module::Build::ModuleInfo->new_from_module($mod);
         my $version = $info->version;

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

         # via Module::Build
         my $info = Module::Build::ModuleInfo->new_from_file($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-Install/>

       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.