No discussion of sets would be complete without someone mentioning Quantum::Superpositions, from Damian Conway (TheDamian...yes, really that damian).

It's a sick and humbling module, yet one of the coolest things I've played with, and I couldn't begin to do justice to describing its features. Every time I wade through its intreguing documentation I find something new that I hadn't noticed before. You may find it useful to read the section on Boolean evaluation of superpositions, for example.

Enjoy!