Forwarding mail

Hi. I'm trying to have mail that I receive at my shell account forwarded to my 
pop account mailing address.
What I'd like to happen is that when mail comes in to the shell account I'd 
like the subject changed to something like "Shell mail." so that when it gets 
sent to the other account it can be put in to a folder for archiving. Can this 
be done, and if so how would I do this?

Thanks for any help you may be able to offer.