Or even simpler:

perl -debug
[download]

which puts you into the debugger debugging a program consisting of bug;!

Warning: this works only on recent Perls, probably 5.004 and later. Whichever Perl where you could nestle the code up against the -e switch. Prior to that, you had to so something like:

perl -de 0
[download]

-- Randal L. Schwartz, Perl hacker