Assuming you have a shell account on a Unix machine, in addition to procmail you can use Mail::Audit to intercept and process incoming messages before they're appended to your mailbox.

Simply¹ write a Perl script that uses Mail::Audit, and drop a command line to invoke that script into ~/.forward

¹ With the standard caveat that you should test the bejeezus out of any script that might interfere with your getting your email.