Well I am in muddle, because I didn't take the time to really make the things just "right". However I test each new small code block (using small test scripts) while I write it, and I check that it pass perl -c every 5 seconds, and I stop to test the code I just wrote after 20 minutes max -- so it's not that bad actually; it pretty much works, but the apps I'm working on are very complex, multi-process (with possible deadlocks...) data management systems...
So now that I'm about to close a project and while I'm already working on the next one (this one very late too, of course :) I'm trying to meditate about it to make it much better than the previous one :)