It works pretty much the same in all OO languages, just because you make a class Bar that is a subclass of Foo, doesn't mean Foo->yada creates Bar objects, Foo->yada does what it did before

If the original class is not meant to be subclassed, and you want to subclass it, you'll have a lot of work ahead of youand you want to sub

Modern Perl discusses "Redispatching Methods in AUTOLOAD"

but from what I can guess of your question, you don't need subclass or redispatch