It would have been nice of you to shortly describe, what Predicate Dispatch is. At least according to what Google tells me, Predicate Dispatch seems to be (object/class) method dispatch based on functions ("predicates") that indicate which method is the most appropriate to dispatch to.

The Perl5 dispatch mechanism has only single dispatch based on the object/class type, and Perl6 will have multimethod dispatch, based on all parameter types, as far as I understand. Implementing and (much more so) sensibly declaring Predicate Dispatch methods is something I haven't seen, but the most likely candidate for an implementation is Damian Conways book, ?Object Oriented Perl?.