clean inside Subject? Rated 2 out of 5 stars

works nice, but I receive some mail through a listserver, which removes its '[xxx]' tag from anywhere inside the subject line, then adds it back to the front, so that the subject lines appear like:
[xxx] re: Re: RE: aw: ....
re: [xxx] re: Re: RE: aw: ...

It would be nice if I could have a way to preseve that tag (anywhere on the subject line) but ignore it for the purposes of removing prefixes. I tried defining a prefix '(\[xxx\])' that should be recognized as prefix but left alone (everything between () is not deleted). However doing that, it deletes everything after the [xxx] Tag and the actual Subject is also deleted.

This review is for a previous version of the add-on (0.4.1).