The tool you will be using most often is your editor. Pick an editor and learn it inside and out. Every single editor will perform the main function - put text into a file. Every single editor worth talking about will give you shortcuts. It doesn't matter if it's Komodo, Emacs, or some vi clone. Pick one, stick to it, and learn it as well as you can. After 10 years, I'm still learning new tricks for vi.

Testing is another tool you should be using more than you already do. Your test suite is your preventative maintenance. This is what keeps you from screwing up. A friend of mine helped me change my brake pads recently. When we took the tire off to get to the pads, he put it right under the car. When I asked him why, he countered with "Is it cheaper to get a new rim or a new axle?" That's a test case for mechanics.

CPAN is another tool. Recently, someone like japhy wrote a module to fulfill a request (Techniques On Saving Memory). Turns out that not one, but two modules were already on CPAN that did what japhy wrote (though the APIs for each were different). Granted, it was only 30 minutes and japhy probably enjoyed them. But, what if you write your own connection to a database (DBI) or templating module (Template) or web application framework (CGI::Application)? That's not 30 minutes. In some cases, that's 30 weeks and you still won't get it right. And you have to maintain it on your employer's dime.

Keeping with the CPAN idea - learn how to use the modules you do use. Did you know that you can pass in a reference to a subroutine as a <TMPL_VAR> to HTML::Template and it will behave as a callback, even within a <TMPL_LOOP>? That was a feature someone was asking for recently and was considering junking H::T because "it wasn't there". Yet, it was there (just documented in a confusing way). That's huge!