How to implement both object->method and module::function interfa ce?

What's the conventional wisdom on creating a module that supports both an OO
and non-OO interface? Are there any CORE or CPAN modules to serve as a
textbook, or is the anwser "Don't do that"? 

I've got some code that checks the first parameter passed to see if it is a
reference, assumes any reference is an object reference... and then proceeds
accordingly. -It feels pretty sloppy, but it works.

Garrett