I personally have to write a lot of regex a few times a week depending on what I am up too at work, and when I finally got around to attempting to write some for nZEDb, I spent maybe an hours trying to figure out why it wouldn't work on the testing page (never did get it to do anything but they work).
Long story short, I kept switching between a 2 testers, the mysqld cli, testing page, and one of my web scrappers I finally figured out that I wrote it for javascript not for pcre.
Feel pretty stupid now, even though for some reason the Release Naming Regex Test is not working for me (admin/release_naming_regexes-test.php?action=add).
Just glad I got it figured out, only if there was a way to add multiple different groups I would be really happy.