Package variables are the worst, because their scope transcends a single file.
How are package variables worse than file-scoped lexicals? If it's because it allows people to mess with parts of your code that you didn't intend, then why use a package variable instead of a file-scoped lexical? (Yes, there are a few rare legitimate reasons.) If you have a legitimate reason for using it but it's not a part of the interface, is it bad because you feel a need to "protect" your variables from users? (If that's the case I guess regular subroutines are bad too.) If you have it like a package variable because it's a part of the interface, then it's not evil. Those are the cases I can think of where I'd use package variables in modules, and I can't figure out why you think package variable are "the worst". Can you elaborate?
See perltoc if you don't know which perldoc to read!