New to MP3Tag

Just started tonight and been reading and Regexp are very powerfull stuff. So here is a VERY basic ?.. I kinda of think I know but trying to get a help in the first few days and I should be on a better track as I learn everything..

So the Basic Idea is that MANY of mp3's are not tagged, so to start I'm only concerned with Artist and Titles... My Goal is to take about a 500 untagged files and apply a Filename to Tag Operation however the basic %artist%- %title% is not going to work so I would need to throw in other formats as I have file names such as
Artist - Title
Artist - Title

and a few more which I can work on once I see how it would be the best way to Implement this.

if you need these different patterns then read in all your files but apply a filter next that refects the pattern.
A filter for the first type of files would look like this:
%_filename% MATCHES .* - .*
Select these files and call up "Filename - Tag"
Enter a pattern that looks like this:
%artist% - %title%

The next set of files would be filtered by

%_filename% MATCHES -
The "filename - tag" pattern would look like this
%artist% - %title%
and so on. I hope you can manage now.