Module::CoreList contains the hash of hashes %Module::CoreList::version,
this is keyed on perl version as indicated in $]. The second level hash
is module => version pairs.
It also contains %Module::CoreList::released hash, which has ISO formatted
versions of the release dates, as gleaned from the perlhist manpage.
Submitted by: Autrijus Tang <autrijus@autrijus.org>
