Private Message Script - Perl/MySQL

Hi,
I'm looking for a perl private messaging script that can be used by students (registered users) to contact their teacher (admin user). I want all of the features of a web based mail system like folder system, attachments, spell check, etc. with the exception that everything will be for internal use (e.g Mail cannot be sent outside the system. Like the private message system built into many forum/bbs scripts).
I looked at some full blown web based email scripts (like hotmail/Yahoo style) but they are probably an over kill for what I want and I don't think I can limit the users to only be able to send messages to their teacher.
Can anyone recommend a good (Perl/MySQL) internal messaging system script or should I have it made to order?
Thank you.