mailing list filter, prepends to header, runs slow

This is intended to make reading vast quantities of mail easier; it
prepends to the subject header based on the mailing list it originates
from (where the majority of mail comes from).  It makes deleting
messages I don't want to read easier.  The recipe seems to work fine,
but it's quite slow, and I'm wondering if there may be a way to speed
it up a bit?  It seems that the speed hit takes place more with the
two formail strings than with the pattern matching, as would be
expected.  If I leave in the conditions but have empty actions
(i.e. recognize pattern but do nothing), there is almost no speed
reduction when compared to using no *rc file at all.  I suspect that
there is no way to increase execution outside of upgrading hardware,
but am hoping I will be pleasantly surprised :)

The general pattern is as follows

# initial environment

        PATH=/bin:/sbin:/usr/bin:/usr/sbin
        LOGFILE=$HOME/procmail.log
        SUBJECT=`formail -xSubject:`

# mailing lists

        SUBJTYPE='whatever I want to prepend for this mailing list:'
        :0 f
        * condition unique to the particular mailing list for which\
          I am prepending
        | formail -i "Subject: ${SUBJTYPE} ${SUBJECT}"

        <a couple dozen other lists...>

# end

Thanks greatly...

Scott