sp.exe is pretty cool, i'll keep that in mind for the next time someone asks for a wallpaper changer
I'm not sure where you could get more info about this. Maybe a search for "alias" or "groups" here in the find and run forum would get you some interesting results. Another interesting search would be "regex" or "regular expressions".
Most definitelly, it's very useful to have regex, it can solve a bunch of problems, sometimes.