|Perl: the Markov chain saw|
parrot is currently too slow to be an efficient competitor, there's not much progress, and there was heavy mismanagement. Feature-wise it is an interesting alternative.
But there is a lot going on.
Larry is already writing a p5 grammer for perl6/nqp, and had with MAD a working
perl6 is quite perl5 compatible, with much more features and better performance than perl5 for complicated use-cases, which you would call "Modern Perl" (i.e. Moose, Grammars, ...). But it is totally post-modern perl.
perl11.org (5+6=11) is an umbrella project to try to mix/replace the various parts, parser, compiler/optimizer, runtime. See irc.perl.org #perl11
I am thinking of an implementation based on vmkit to replace parrot or write a better p5 vm, codename p2.
rakudo is working into similar directions, making nqp on jvm or mono or whatever possible.
Perl5 XS is not that big a deal. Either throw it away as it is inefficient and hard to work with anyway. Or provide convenience wrappers. Better languages provide better glue interfaces. Inline e.g. is much better, but you still have to deal with the XS API.