# path to sendmail needs to be correct, this is a good guess
$mail_prog = '/usr/lib/sendmail' ;

open MAIL, "|$mail_prog -t" or die "Can't open pipe to $mail_prog, reason $!\n"
print <<MAIL;
To: $recipient
Reply-to: $reply_to
From: $from
Subject: $subject

$body
MAIL
close MAIL;