Question related to this: Are stringified references used as hash keys unique? That is, if I only ever use them to look hashed values for given references up, do I need to use something like Tie::RefHash? I've gotten into the habit of using Tie::HashRef whenever I use references as hash keys. I realize now that in many cases I'm never trying to dereference the keys -- only take a reference and find its hashed value. So in the case above, I probably don't need a tie and I can therefore weaken the self referential reference I'm using as a key. The hash in question is always hashing references to bless'ed hashes of the same object (package) type.