#!/usr/bin/perl
use warnings;
use strict;

my $mailprog ="/usr/sbin/sendmail";
my $mailflags ="-t -n -oi";
my $recipient = 'recipient@domain.com';
my $msg_goes_here = "you're message";

open  SENDMAIL, "| $mailprog $mailflags" or warn $!;
print SENDMAIL "From: user\@domain.com\n";
print SENDMAIL "To: $recipient\n";
print SENDMAIL "Subject: testing 123\n\n";
print SENDMAIL $msg_goes_here;
close SENDMAIL;