I just want to say that I REALLY, REALLY like this module. It's amazing. I'm impressed that there is support for foreign classes. And I'm trying not be negative.

Having said that, what are the consequences of just doing a "use base" to get the modules on the @ISA array? Would this break the Object::InsideOut module?

My pure virtual class PVC doesn't have a "new" subroutine. A pure virtual class just provides a list of subroutines that all subclasses should implement. Furthermore, PVC doesn't make any commitment to the representation of the blessed object. You could have an inside out subclass and a hash-based subclass that are PVCs. Likewise, it doesn't make sense to create an object from a pure virtual class, because the subroutines are not implemented. See the Class::Virtual module.