Allow negative filtering through regexp filter

[VojtechDostal]

It would be really really helpful if one could do negative filtering using RegEx. Currently, if I understand correctly, only expressions like this are allowed:

^(Wayside crosses)(.*)$

But what if I want anything BUT Wayside crosses? I am not a programmer but I envision this could be done by a) adding new RegEx functionalities or b) allowing Regexp filter as one of the inputs for the field Combination (eg. "categories NOT regexp")...

thank you for consideration