in reply to HTML email with attachments

The docs provide an example on how to do this:

    $msg = MIME::Lite->new(
                 To      =>'you@yourhost.com',
                 Subject =>'HTML with in-line images!',
                 Type    =>'multipart/related'
                 );
    $msg->attach(Type => 'text/html',
                 Data => qq{ <body>
                             Here's <i>my</i> image:
                             <img src="cid:myimage.gif">
                             </body> }
                 );
    $msg->attach(Type => 'image/gif',
                 Id   => 'myimage.gif',
                 Path => '/path/to/somefile.gif',
                 );
    $msg->send();

[download]

Notice the URL is cid: followed by the value specified in the image's Id field.

In Section Seekers of Perl Wisdom