A VM for Perl should have common Perl operations be single units in the VM. For instance Perl does a lot of hash lookups. That should be an opcode.

Java's VM creates something much closer to a virtual machine. (Note that not only does Java's VM not define a hash lookup as a basic operation, but Java doesn't either!) This is a bad fit for what Perl spends its time doing, you want your basic operations to be as fast as possible, and you want basic operations that can be mapped well to the Perl code.

Incidentally Perl 5 already has what is for all intents and purposes a VM. For obvious reasons that is a far more appropriate model for Perl 6 than Java's would be.