Just use Mail::SendEasy. It just works very well with HTML messagens and attachments. Also is easy to install, since it doesn't have dependencies.

Here's an example of use:

  use Mail::SendEasy ;

  my $mail = new Mail::SendEasy(
  smtp => 'localhost' ,
  user => 'foo' ,
  pass => 123 ,
  ) ;
  
  my $status = $mail->send(
  from    => 'sender@foo.com' ,
  to      => 'recp@domain.foo' ,
  subject => "MAIL Test" ,
  msg     => "The Plain Msg..." ,
  html    => "<b>The HTML Msg...</b>" ,
  ) ;
  
  if (!$status) { print $mail->error ;}
[download]

In the example above it's sending a multipart message, with a text and a HTML version at the same time. Soo, you don't need to care about the MIME message. ;-P

Good luck. ;-P