use MIME::QuotedPrint;
use MIME::Base64;
use Mail::Sendmail 0.75; # doesn't work with v. 0.74!

%mail = (
         from => 'you@domain.tld',
         to => 'whoever@someplace.tld',
         subject => 'Test attachment',
        );
        

$boundary = "====" . time() . "====";
$mail{'content-type'} = "multipart/mixed; boundary=\"$boundary\"";

$message = encode_qp( "Some message" );

$file = $^X; # This is the perl executable

open (F, $file) or die "Cannot read $file: $!";
binmode F; undef $/;
$mail{body} = encode_base64(<F>);
close F;

$boundary = '--'.$boundary;
$mail{body} = <<END_OF_BODY;
$boundary
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

$message
$boundary
Content-Type: application/octet-stream; name="$^X"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="$^X"

$mail{body}
$boundary--
END_OF_BODY

sendmail(%mail) || print "Error: $Mail::Sendmail::error\n";