You can find more information on the speaker's site:
One of the tried and true ways of debugging is to sprinkle 'print "Here! $val\n"' around and see what happens or if the program even reaches that point. Simple and effective! Carp::REPL lets you take this a step further by starting an interactive read-eval-print loop (REPL) at an arbitrary point in your program.
I've taken this technique and mixed in a splash of Continuity to build an interactive web-based REPL and inspector for your application. It works on CGI scripts too (baring some fixable browser timeouts :) ). If you're nice to it, it might even let you edit your source file, reload it, and continue execution. You just add a single "inspect()" where you like and you'll be whackin' those bugs DOWN!
In this talk I'll show you how to use the tool and how it's built... and how you can add to it. And by then it'll be on CPAN :)