Blat requires you to use a temporary file for the message portion of the email. These links should help you along your way.

http://gepasi.dbs.aber.ac.uk/softw/Blat.html
http://www.interlog.com/~tcharron/blat.html

However, I would consider lachoy's suggestion of using Mail::Sendmail as it makes what you want to do easier and you will end up with more time for fun.

Enjoy,

EEjack