is your friend. Do a PerlMonks search on "Win" to find a few of the gimmes'n'gotchas.
The biggest thing to be aware of is that a lot of things that Unix lets you get away with, Windows won't. A lot of things Windows forces you to do may or may not break your Unix code. There is a way to tell what OS you're on, but I would be very careful about sprinkling your code with it. That's a good way to give yourself heartburn.