I am religious about avoiding having a hash and a hashref in scope with the same name. That way lies insanity and (a couple of refactorings later) hard to track down bugs.
Comment on Re^4: Stupid mistakes I repeatedly make
Oh, I didn't actually have a hash and hashref in the same scope with the same name. Two functions, one with a hash, the other with a hashref, and me not paying attention to which was which. Nothing use strict couldn't find immediately.