(*720p* !iswm $2) is what ignores the 720p part. That little bit checks to see if "720p" ISN'T in the $2, and if it isn't, continues on with the code.

Line 3 replaces the TV+/ with "$null" (or .. nothing, essentially) and sets THAT result to %rl. Could have easily just used $remove, but eh, there are many ways to accomplish the same thing. Hopefully that works, though