Setting variables based on header content? (Is it possible?)

I would like to write a recipe to "improve on" this:

> :0
> * ^Subject: .*cvs-all-digest
> | formail +1 -a "Message-Id: " -a "Sender: 
> owner-cvs-all(_at_)freebsd(_dot_)org" -ds >>F/cvs
so that I could copy the Message-Id: line from the digest message into
each of the bursted messages.

Is that possible?

How?  I've tried all the magic I can think of (pipes, etc) but nothing seems
to do what I wish to accomplish.


Thanks in advance for your help,


joe stein