2+ years on since I wrote "Toolkit review: Devel::Local, Devel::SimpleTrace, Reply" and I've got a couple more suggestions. I still use Devel::Local a lot but for something more substantial than quick hackery I use mst's App::Myperl.

I don't use Devel::SimpleTrace much anymore.. I switched to Devel::Confess since watching haarg talk about writing it in a video that I can't find right now. Lastly I still use Reply but I've added Toby Inkster's Pry to my secret weapon list. It makes dropping into a Reply interactive session super easy. ( Use pry; pry(); )