There is always the built-in perl debugger, which as you probably know is invoked with the -d flag. I think you can set breakpoints and watch execution. I heard however, that Larry Wall himself does not use it! (Wasn't that in the second Apocalypse?) Anyway, I have also heard that Komodo has a nice interface, if you are using Win... I personally have only used vi (and am probably missing out on the fancy stuff!)...

I love the beginning of the perldebug man page. It says: first of all, have you tried using the -w switch?