Judging from your code, you appear to be running on
http://www.hypermart.net.
On their site they say they have
Mailtools and
Mime-Tools installed for paid users.
MIME::Lite is included therin, and should take care of everything you need, and if not, those packages include more advanced tools. (I haven't used
Mail::Sendmail recommended by others, but
Mail::Mailer is included in
Mail-tools and has gotten very good comments from others on this site.
All the comments mentioned here (and those in reply to you previously at Dangers of rolling your own mail script) apply, so I recommend using one of those modules, particularly for something as sticky as attachments.