[SpamCop-List] A PROCMAIL expression to prepend/append a subject line of a message header?

[Ben]

Anyone know how to write a PROCMAIL expression to prepend/append a 
subject line of a message header?

I know how to add a line; for example:
X-Suspected-Spam: Caught by spamfilter2.rc, GROUP 2  Score: 5530/100

  #=-=-=-=- It's done with this expression.
      {
      PATSCORE=$=
      :0 fhw
      | formail -A "X-Suspected-Spam: Caught by spamfilter2.rc, GROUP 2 
  (Score: ${PATSCORE})\/100 "
      :0:
      $SPAMBOX
      }
  #=-=-=-=- end.

What I want to do instead is take an existing subject line and inject a 
phrase or score. That is to change a line.

For example; the subject in the header would change from:
Subject: We have a simulation to run.
And could be changed to
Subject: [suspect spam:  233.points] We have a simulation to run.
Or  --> Subject: [RBL bl.spamcop.net] We have a simulation to run.
This would be ok but the latter is better.  -->  Subject:  We have a 
simulation to run. [RBL bl.spamcop.net]
    Etcetera.

I am misunderstanding something in formail and procmail.