Forwarding beginning of messages

Dear All,

I am new to procmail. I am trying to write a recipe that sends a copy of
all my mail to a second account, however, I would like those e-mail longer
than, say, 10K, to be truncated and only the first 100 lines forwarded
(the header should be intact, thogh). Is there a simple way to do that
(using formail, I guess), in such way that the message gets forwarded with
the original "From:" ? 

Any suggestions welcome,

Adriano Barenco
barenco(_at_)physics(_dot_)ox(_dot_)ac(_dot_)uk