[Mimedefang] attachment detection

[John Nemeth]

     I need to convert this procmail recipe for use in
mimedefang-filter:

:0BHc
* !^X-Spam: YES
* !^X-Loop: TRUE
* ^Content-Type: multipart/mixed;
| formail -a "X-Loop: TRUE" -i "To: mailchk" -i "Subject: *** Attachment *** " -
I "Apparently-To: " -I "Bcc: " -I "Cc: " | /usr/lib/sendmail -t -oi

I'm thinking of putting something like the following at the end of
filter_end():

if ($entity->mime_type eq 'multipart/mixed') {
  add_recipient('mailchk');
}

Would the above do the trick?  I realise that it isn't quite the same
thing and that I would have to generate a new message in order to
change the headers.