For dealing with attachments use one of the perl MIME modules. I find that MIME::Lite has been strong-enough to do anything I've ever needed with attachments/multipart messages. Here's an example of its usage taken from the MIME::Lite documentation:

       use MIME::Lite;

           # Create a new multipart message:
           $msg = new MIME::Lite
                       From    =>'me@myhost.com',
                       To      =>'you@yourhost.com',
                       Cc      =>'some@other.com, some@more.com',
                       Subject =>'A message with 2 parts...',
                       Type    =>'multipart/mixed';

           # Add parts (each "attach" has same arguments as "new"):
           attach $msg
                       Type     =>'TEXT',
                       Data     =>"Here's the GIF file you wanted";
           attach $msg
                       Type     =>'image/gif',
                       Path     =>'aaa000123.gif',
                       Filename =>'logo.gif';
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Once you have your message constructed with attachments then you need to send it. I prefer to use Net::SMTP to send messages, but there are several other perl modules that can send mail (and several ways of just doing it by hand). If you're already using MIME::Lite the easiest method is to use its built-in send function:

        $msg->send;
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If you're interested in delving deeper, O'Reilly has a decent book entitled Programming Internet Email that covers most of the interesting internet e-mail protocols and formats. It has a good chapter on e-mail related Perl modules.