module to determine modules shipped with perl

 Module::CoreList is a Perl module that can provide various information about
 the versions of Perl modules that shipped with perl interpreter releases.
 .
 It contains a hash of hashes which is keyed on the perl interpreter version,
 as indicated in $]. The second level hash has pairs of modules and as well as
 their versions. It's possible that the version of a module is unspecified, in
 which case it will be undef.
 .
 Other features include a hash providing ISO formatted versions of the release
 dates, as gleaned from perlhist, and a hash that clusters known perl releases
 by their major versions.