This may be a little bit of an unusual request but I'm using an RSS feed reader that has a filter built in that can read regex expressions. What I've been trying to do is configure it to filter everything except this

(\w \W ){1,5}-

Where I'm having issues is that the program is very limited in how it executes the code. The only options there are are choosing the field that the filter reads (Title, body, link etc), how the filter reads it (contains word, does not contain word, starts with word, etc. This is also where the regex option is and you can't pick more than one option, otherwise I could have done regex and "does not contain" and be done with it), and finally what the filter does (mark news as read, saves it to favorites, delete etc).

What I want essentially is something in the regex language itself so that it reads that code I'm using and marks everything except it as read. I'm very much a layman when it comes to coding so I'd appreciate any help.