I think the Perl 6 developers figured that out a few years ago, and ended up implementing MoarVM, instead of using or building a more generic VM. One can implement other languages in MoarVM, but it's been built for Perl 6, so it fits Perl 6 best. Maybe it isn't a super "tight" integration, but it's much tighter than something like Perl 6 on the JVM could ever be.