[Dovecot] OT: Run Sieve On A Mailbox Manually

(Apologies for being offtopic.)

The subject basically says it all...does anyone know of a tool to run
a sieve script on a mailbox (in particular, Maildirs) manually?
Ideally, I'd like to do it without adding a bunch of new headers to
the mail.

So, could I just do a find (or for-loop, if it was just one maildir)
command and pipe all the mails into deliver..?

Thanks, Neil.