I just found a very good online regex tester and debugger: https://regex101.com/

The nice thing is that you can register and then save the your regular expressions for later use. It even keeps a history in case you chance a previously saved regexp. From author

I have no plans of ever clearing the database (unless it grows incredibly large, which it hasn't) which means the expressions you save should last forever.

More details can be found on GitHub

Screenshot of regex101 user interface