I'm thinking X, you're thinking Y: more food for the FAQ. There are different problems to be solved.
in reply to Re^4: Using hashes for set operations...
in thread Using hashes for set operations...
Stringification on an object: The overloaded stringify function might not be what you want for this specific call to intersection. Just like you can sort different ways, you want to identify matches some custom way for this operation alone.
I'll read those links and reply more later. (Oh, that's not a link, it's an unescaped [).