Don't import anything and use namespaces to be explicit where every function is coming from..
(Ok, this is more of a pet-peeve/stylistic concern than anything else, but I think it's vastly clearer where "Util::random_func" is coming from. People can be reasonably espected to memorized/recognize most of the perl builtin functions, but expecting them to recognize/learn all the random functions that every module can export is pushing it a bit. This way when you go back to your 10,000 line application, you know exactly where every function is defined.)