Oh Perl 5-6 interopability was actualy promised at the very beginning - it was framed as "automatic translation" I think the problem that can't be dolved is only perl 5 can parse perl 5! There's other projects to make this happen (like: use v5;)
Calling a Perl 5 module from Perl 6 can work I believe ( as well as other languages!), which is somewhat of a miracle. But it's interfaced using Perl 6.
> Supports Perl 5 modules including XS modules. Allows passing integers, strings, arrays, hashes, code references, file handles and objects between Perl 5 and Perl 6. Also supports calling methods on Perl 5 objects from Perl 6 and calling methods on Perl 6 objects from Perl 5 and subclass Perl 5 classes in Perl 6.
Calling a Perl 5 module from Perl 6 can work I believe ( as well as other languages!), which is somewhat of a miracle. But it's interfaced using Perl 6.