I'm not really a programmer, and perlmonks has introduced me to a lot of very smart programmers and the "programmerly" techniques they use, things that have made my code better, more reliable and easier to write, like:

• automated testing (with Test)
• test coverage (with Devel::Coverage)
• code profiling (with Devel::DProf)
• object inheritance (understood the concept, learned how to use it in perl right here).