This is what is working for me
### Create the multipart container
$msg = MIME::Lite->new (
From => $from_address,
To => $to_address,
Cc => $to_cc,
Subject => $subject,
Type =>'multipart/mixed'
) or die "Error creating multipart container: $!\n";
### Add the text message part
$msg->attach (
Type => 'TEXT',
Data => $message_body
) or die "Error adding the text message part: $!\n";
### Add the xls file
$msg->attach (
Type => 'application/xls',
Path => $my_file_xls,
Filename => $your_file_xls,
Disposition => 'attachment'
) or die "Error adding $file: $!\n";
### Send the Message
MIME::Lite->send('smtp', $mail_host, Timeout=>60);
$msg->send;