Get extra arguments from subject line

hello everyone!

how do i get extra arguments from the subject like this:

:0
* ^Subject:.*get assign <number>

where <number> is the variable that i want to use in:

| (formail -r -A"X-Loop: my_email" ; cat $HOME/assign/<number>) \
  $SENDMAIL -oi -t

---
u s l s N E T   university of st. la salle, bacolod city, philippines
. . . . . . .   PGP key available via e-mail / subject: get PGP key
francis vidal   tel. nos. (6334).435.2324 / 433.3526