Yes, you can send emails that contain a section of content that is of type 'text/html' and another that is 'text/plain'. Many of the modules available for sending emails describe this in their documentation; for instance, Mail::Sendmail specifically mentions doing this in its FAQ (with sample code), and MIME::Lite includes information on sending HTML in its documentation.

HTH.

Update: 24 Aug 2005 - s/speficially/specifically/