delete/archive old mail

Hi everybody, I store user's mail in the old mbox format. I have many scripts to manage users that works fine with mbox. I use the very old Expire_mail.pl script to delete mail older than NN days for selected users (nightly cron job). Still works fine with my CentOS dovecot-2.0.16. Now I want move the mail to a sort of archive folder instead of simply deleting it from the inbox for some users. Is there a similar script or some simple triks?

Thanks, F.