In addition to mentioning the command line debugger, you could mention the very nice support for perldb in Emacs. I blogged about this recently when I made PerlySense debugger-aware (the PerlySense docs contain a summary of the most common debugger operations).
in reply to RFC: Basic debugging checklist
A while back I blogged about how to limit the output when dumping huge data structures with Data::Dumper and the debugger x command. Feel free to incorporate any of that in this post. In particular the syntax of the .perldb config was nontrivial to figure out, so that may be useful to someone.
That concludes the shameless plugs for today :)