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CPAN::Meta::Prereqs(3perl) Perl Programmers Reference Guide CPAN::Meta::Prereqs(3perl)


CPAN::Meta::Prereqs - a set of distribution prerequisites by phase and type


version 2.150010


A CPAN::Meta::Prereqs object represents the prerequisites for a CPAN distribution or one of its optional features. Each set of prereqs is organized by phase and type, as described in CPAN::Meta::Prereqs.



  my $prereq = CPAN::Meta::Prereqs->new( \%prereq_spec );

This method returns a new set of Prereqs. The input should look like the contents of the "prereqs" field described in CPAN::Meta::Spec, meaning something more or less like this:

  my $prereq = CPAN::Meta::Prereqs->new({
    runtime => {
      requires => {
        'Some::Module' => '1.234',

You can also construct an empty set of prereqs with:

  my $prereqs = CPAN::Meta::Prereqs->new;

This empty set of prereqs is useful for accumulating new prereqs before finally dumping the whole set into a structure or string.


  my $requirements = $prereqs->requirements_for( $phase, $type );

This method returns a CPAN::Meta::Requirements object for the given phase/type combination. If no prerequisites are registered for that combination, a new CPAN::Meta::Requirements object will be returned, and it may be added to as needed.

If $phase or $type are undefined or otherwise invalid, an exception will be raised.


  my @phases = $prereqs->phases;

This method returns the list of all phases currently populated in the prereqs object, suitable for iterating.


  my @runtime_types = $prereqs->types_in('runtime');

This method returns the list of all types currently populated in the prereqs object for the provided phase, suitable for iterating.


  my $new_prereqs = $prereqs->with_merged_prereqs( $other_prereqs );
  my $new_prereqs = $prereqs->with_merged_prereqs( \@other_prereqs );

This method returns a new CPAN::Meta::Prereqs objects in which all the other prerequisites given are merged into the current set. This is primarily provided for combining a distribution's core prereqs with the prereqs of one of its optional features.

The new prereqs object has no ties to the originals, and altering it further will not alter them.


    my $new_reqs = $prereqs->merged_requirements( \@phases, \@types );
    my $new_reqs = $prereqs->merged_requirements( \@phases );
    my $new_reqs = $prereqs->merged_requirements();

This method joins together all requirements across a number of phases and types into a new CPAN::Meta::Requirements object. If arguments are omitted, it defaults to "runtime", "build" and "test" for phases and "requires" and "recommends" for types.


This method returns a hashref containing structures suitable for dumping into a distmeta data structure. It is made up of hashes and strings, only; there will be no Prereqs, CPAN::Meta::Requirements, or "version" objects inside it.


This method returns true if the set of prereqs has been marked "finalized," and cannot be altered.


Calling "finalize" on a Prereqs object will close it for further modification. Attempting to make any changes that would actually alter the prereqs will result in an exception being thrown.


  my $cloned_prereqs = $prereqs->clone;

This method returns a Prereqs object that is identical to the original object, but can be altered without affecting the original object. Finalization does not survive cloning, meaning that you may clone a finalized set of prereqs and then modify the clone.


Please report any bugs or feature using the CPAN Request Tracker. Bugs can be submitted through the web interface at <>

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


  • David Golden <>
  • Ricardo Signes <>
  • Adam Kennedy <>


This software is copyright (c) 2010 by David Golden, Ricardo Signes, Adam Kennedy and Contributors.

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

2024-03-06 perl v5.38.2