Well, Pugs has some issues with running Perl 5 modules atm., but that functionality is specced, so ever "official" implementation has to implement that as well.
I don't know, but last I heard... wasn't $Larry working on a 5-to-5 translator which should be the basis for a 5-to-6 one? IIRC he stated that the goal was to have it working 90% of the times, doing it right also 90% of the times, or something like that.
Re CPAN, I quoted it before but I'm doing it again here: "CPAN is my programming language of choice; the rest is just syntax." (Audrey Tang)