the venerable print for anything up to 300 lines or so.
One window taking up most of the screen vim'ing the script, and one smaller window where I run the script and watch the output. It's sweet.
Once I really need to step through code, I use The Open-Perl-IDE, a free debugger for windows. One quirk I have noticed is it doesn't seem to like DBD connections. Oddly, I recently got a chance to try out Komodo, and it didn't like scripts that used DBD either. Both the OpenPerl IDE and Komodo would barf with an error in an internal file.
print and printf are rock solid. Primitive, but there's no learning curve to use them, no bugs in them, and they're everywhere I'll ever find myself writing code.