Previously my testing would be done by printing variables and return values of functions, relying on my eye to catch any issues. While serving me well it wasn't very good for my productivity. Since writing tests (using Test::More and Test::Exception) I've been able to write more code, with increased confidence, and better results
Now I need to create test suites for our web application using WWW::Mechanize and get the other developers on my team to buy into them. Wish me luck (although I shouldn't need it).