require MIME::Lite;

$msg= MIME::Lite->new(
  From    => $from_addr,
  To      => $to_addr,
  Bcc     => $bcc_list,
  Subject => $subject,
  Type    => 'multipart/alternative',
);
$msg->attach(
  Type => 'text/plain',
  Data => $some_plain_text,
);
$msg->attach(
  Type => 'text/html',
  Data => $some_html,
);