open(SENDMAIL, "|/usr/lib/sendmail -oi -t") || die "Cannot open sendmail output"; 
 
print SENDMAIL <<"ENDENDEND"; 
From: <test\@test.com> 
To: <test1\@test1.com> 
Subject: report spam 
MIME-Version: 1.0 
Content-Type: multipart/mixed; 
 boundary="DeathToSpamDeathToSpamDeathToSpam" 
 
This is a multi-part message in MIME format. 
--DeathToSpamDeathToSpamDeathToSpam 
Content-Type: text/plain; charset=us-ascii 
Content-Transfer-Encoding: 7bit 
 
 
--DeathToSpamDeathToSpamDeathToSpam 
Content-Type: message/rfc822 
Content-Disposition: attachment 
 
ENDENDEND 
 
while (<STDIN>) { 
  print SENDMAIL ; 
} 
 
 
print SENDMAIL <<"ENDENDEND"; 
 
--DeathToSpamDeathToSpamDeathToSpam-- 
ENDENDEND 
 
close (SENDMAIL);

To: <test1\@test1.com test2\@test2.com test3 ...>

man sendmail