For most modules, I would agree that it's not worth the effort. With Test::Harness, it's worth it if we can do it with minimum pain. The main problem is the concerns that we can get performance benefits from pre-compiled regular expressions with qr//. Performance is one of our biggest issues (we're pretty damned close, though), and if a 5.004 patch is supplied which is minimal impact and doesn't hurt performance, we'd strongly consider it. (Hell, I'd consider a factory class instantiating "version" subclasses on demand if that's what it took, but there are other problems with that which are beyond the scope of this reply).