That's funny. Just yesterday I needed that and used pythex and a bunch of other similar 'testers' to make sure my regular expression was good. It was, but it somehow didn't work on the Mozilla Add-On Builder.

After asking a question on the #jetpack channel, members have spotted the mistake: The regex was correct, but it needed to "match the exact string" as mentioned on the doc. I've read it, but didn't understand that point. There was a missing "." at the beginning and the end. So /.regex.*/

Thanks for putting this.