Vim with Perl support compiled in makes me happy. The perldo Vim command is nice so I don't have to keep switching back and forth between thinking in Vim-style regex syntax and thinking in Perl-style regex syntax. Especially when I'm writing Perl, it's sometimes hard to make that mental switch.

So yeah, I'm a big fan of using Perl to help write code. Bang out a one-liner or two to spit out a bunch of HTML or rename a file full of variables or whatever. The only bad thing is resisting the urge to start copy/pasting code rather than re-factoring the code itself to make it shorter. Sometimes Vim + Perl makes it TOO easy to edit code.