Well, I think use strict; does usually help to improve the structure of the code. If only because you have to think whether you want something to be global or local (lexical). Sure, you can declare all your variables on top of your script with "my" and keep all the bad habits, but it's somewhat less likely to happen then if you don't start using strict at all.

So it's not going to make your code magically better, but it's going to nag you to make it better yourself.