Don’t get me wrong current Listary syntax is not bad but it lacks a lot off powerful features present in regular expressions. And almost all software I use on daily basis supports it, e.g. Directory Opus, Notepad++, …, so I think it would be really great if you would add it to Listary too. I’m sure a lot of power users will be happy to see this feature in your product. Also regex is relatively easy to implement.
BTW I bought Pro version, I hope this will help you to further improve this application.