ptkdb is also a slick GUI debugger, and it works on Linux, HP-UX, windows, etc. It has hovering, watch variables, breakpoints, stepping, etc.

I really like debugging cgi programs with it. In X-Windows I set the $ENV{DISPLAY} in the BEGIN block and call ptkdb in the shebang:

#!/usr/bin/perl -d:ptkdb
$|++;
BEGIN { $ENV{DISPLAY}; }
[download]

You can single step or set breakpoints in your cgi and watch the output get rendered in your browser as you go.

It should work perfectly the first time! - toma