my $snd = Mail::Sender->new({
    smtp => ...,
    from => ...,
});

$snd->OpenMultipart({
          to => ...,
          from => ...,
          subject =>"TEST",
}) or

    die "Error: $Mail::Sender::Error\n";

$snd->Body(0,0,'text/plain');
$snd->SendLineEnc('TEST EMAIL');

$snd->Attach({
           description => "ATTCHMENT",
           ctype => "text/plain",
           disposition => "attachment; filename=\"xyz.txt\"; type
                            +=\"text/plain\"",

}) or
    die die "Error: $Mail::Sender::Error\n";

$snd->Part();
$snd->SendLineEnc('CONTENT OF ATTACHED FILE');

$snd->Close;