perl5: improve / reimplement packaging

[mojca (Mojca Miklavec)]

I'm opening this ticket to collect and vote on ideas with their pros and cons about different options to package:

• perl5[.x]
• perl modules p5[.x]-foo
• ports that depend on Perl
• perl6

Desired features:

• easy updates of perl modules, possibly (semi-)automated from metadata from CPAN
• painless upgrades from perl5.[n] to perl5.[n+1]
• reasonably small effort with modifying and revbumping all the ports that depend on Perl

Some particular aspects to think about:

• a port could have a flag (possibly "auto-generated") to indicate that there is no difference in what Perl version is being used (other than maybe path to perl, but path could be version-neutral); those ports won't need any revbumps after changing the version
• ...

Please try to think out of the box and and come up with proposals even if implementing them is not yet supported by the base. We can extend the base if we know exactly what we want to achieve.

(No need to rush into any decisions and implementations before we carefully think of all the consequences of that particular implementation.)