OT: Procmail help

[Peter Loron]

Sorry for the OT post.

I'd like to create (or borrow) a Procmail recipe that will add a bit of 
text to the beginning of certain Subject headers. Specifically, I get 
some mailinglists that prefix their messages with something like 
"[listname]", and some that don't. I want to add those prefixes.

I did some looking in Google, but either got back waaaaay too many hits 
or nothing, depending on my keywords.

Can somebody point me to a recipe? I know this wheel has been invented 
before...

Thanks.

-Pete