My understanding is that there is Perl 5 (which is Perl) and a completely separate language known as Raku that was originally supposed to be Perl 6. This happened as Perl 6 took so long (similar to Duke Nukem Forever) that large portions of the Perl community decided it wasn't a realistic upgrade path and the languages had a hard fork.
Perl7 seems to be Perl5 with some changes to the defaults. They can't upgrade to Perl6 as that would be needlessly confusing. If foresight were perfect, Perl6 would have always been a different language name so Perl proper would continue without confusion. The problem was that they had no idea how hard it would be to make Perl6 and thus thought it would be ready in a few years (my understanding) and everyone would upgrade. Raku/Perl6 is SERIOUSLY COOL. I think it just needs a larger community and that's a chicken/egg problem.
Perl7 seems to be Perl5 with some changes to the defaults. They can't upgrade to Perl6 as that would be needlessly confusing. If foresight were perfect, Perl6 would have always been a different language name so Perl proper would continue without confusion. The problem was that they had no idea how hard it would be to make Perl6 and thus thought it would be ready in a few years (my understanding) and everyone would upgrade. Raku/Perl6 is SERIOUSLY COOL. I think it just needs a larger community and that's a chicken/egg problem.