You want sane datetime handing in Perl. You want this module. Does the job. Few odd corners in the API - but leaps and bounds ahead of everything else that I've played with on CPAN for accurate date/time handling.
I've found Perl::Critic an invaluable tool with legacy code - making it very easy to focus down on trouble spots that need immediate attention.
Trivially customisable to make it only complain about the things I care about. Large library of policies on CPAN so I mostly can just pick and choose without having to write my own. Nice API for those few times when I do have to code something myself.
Been an essential part of my toolkit for some time.
The slower a test suite runs, the less likely folk will run it - so Test::Aggregate is a useful addition to my tool set when I've got a traditional set of *.t Perl tests that need to be run more quickly.
When I applied T::A to one $work project I cut 30% off the wall clock time for the core test suite. Useful.
Test::Harness has always been useful - but since the 3.x release we've had something much more flexible that's letting me do some things easily that used to take terribly evil hacks with Test::Harness::Straps. Often just with the standard prove commend line. Nice.
I like this rather a lot. A nice minimal implementation of inside out objects that doesn't get in the way, and doesn't force you to recast your entire OO infrastructure. No source filters, CHECK blocks, etc. so works fine with mod_perl. Nice.
Growl is a rather funky open-source notification framework for Mac OS X. There are several different possible ways of talking to Growl via Perl (Applescript, command line, etc.) and Mac::Growl does a good job of hiding all of this behind a single API. Nice.
Very nice tool for generating simple parsers / screen scrapers. You write a template toolkit template that would generate your content (using a subset of TT commands) and Template::Extract does the rest.