Want to use a blacklist, with one exception

The following recipe, derived from one in the "spambouncer" will (I
think) match any header that contains anywhere a string found in the
maybespam.list.  The change I would like to make is to only search for
those strings in Some parts of the header.  For example, if the subject
line is "cyberpromo's latest trick" I don't want this recipe to match
it.

Also, should I be nervous about any possible problem with the 'zcat
....gz' trick?

# Stuff that gets past the other recipes, but is from a place that
# has spammed me in the past.  (Friends at these places must be added
# to the nobounce file.)
:0
? fgrep -i -f $SBDIR/maybespam.list
* !^X-Loop: noloop(_at_)noloop(_dot_)nlp
  {
  :0 c
  $SPAMFOLDER

  :0
  | (formail -bkrt -A"X-Loop: noloop(_at_)noloop(_dot_)nlp";\
    zcat $SBDIR/maybespam.msg.gz) | $SENDMAIL -oi -t
  }