MIME::Lite makes this very easy:

        use MIME::Lite;
        my $msg = MIME::Lite->new (
               From => 'you@somewhere.com',
               To   => 'someone@somewhere.com',
               Subject => 'A subject line',
               Type    => 'multipart/mixed');

        $msg->attach(
               Type => 'TEXT',
               Data => 'Normal text of the email' );

        # open a file to send
        open FILE "file.zip";
        my $data = <FILE>;
        close FILE;

        $msg->attach(
               Type => 'BINARY',   # or any MIME type you like
               Data => '$data',
               Filename => 'file.zip' );

        $msg->send;
[download]

This link to CPAN will give you lots more info, too.