recipe to strip a suffix from a string

Hello.

Until recently I used to filter messages from
FVWM mailing lists using the following recipe:

   :0:
   * ^Sender: \/owner-fvwm[^(_at_)]*@lists.math.uh.edu
   * MATCH ?? ()\/[^(_at_)]+
   * ? test -d $MATCH || mkdir -p $MATCH
   $MATCH/$MONTHFOLDER

There are 3 mailing lists that I am subscribed to
and that were filtered with the above rule. For
instance, one of them is fvwm-workers, with the
corresponding Sender header line:

   Sender: owner-fvwm-workers(_at_)lists(_dot_)math(_dot_)uh(_dot_)edu

Now the mailing lists have changed and the sender
address has changed the "owner-" prefix to an
"-owner" suffix:

   Sender: fvwm-workers-owner(_at_)lists(_dot_)math(_dot_)uh(_dot_)edu

Please, how should I change my recipe so that
it works with this new schema? In the examplve above,
it should extract the substring "fvwm-workers"
from the address found in the Sender header line.

Regards.

Romildo

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