Messed Up Subject Line??? Help

What is wrong with this: 

I want everything with the word - PEN in the Subject line to not come to my
mail. This is what I put in

:0:
* ^Subject:.*PEN
Junk

It *does* work, but it also throws a bunch of other stuff in the trash as
well. Just random posts seem to get sent to my JUNK file. 

Anyone have a clue?  What is the best way to keep PEN when in the SUBJECT
line, sent to my Junk file?