I might consider using MIME::Entity to do the actual parsing of the message and headers. A few other notes:

• Send a reply to the Reply-To header if it's provided
• Use "X-Loop"-type checks to ensure that you do not enter a mail loop with yourself or another mail robot (e.g. a poorly configured "vacation" script)
• If you're performing any privileged actions, be aware that sender addresses can be pretty easily forged