Today I released a minor update, fixing a couple bugs: "Redo" functionality now works as it should on a Mac via the Command-Shift-Z keyboard shortcut. I've added a group name warning. There's a weird issue with the way the .NET Regex engine allows numeric entries in group names. For instance (?<2>abc)| (?<4>def) will not throw an error upon instantiation. However, when you enumerate through the groups that's when you get a runtime error. So I've added a rule to show a warning in this case that says, "Group names must begin with a word character, or if they're numeric they cannot have gaps between numbers."
Dedicated to the online C# regex tester at regexhero.net