#!/usr/bin/perl
use 5.008;
use strict;
use warnings;

use constant SENDMAIL => '/usr/sbin/sendmail';

my $from = 'foo@bar.example';
my $to = 'blubb@boing.example';
my $subject = 'Some subject';

my $body = "The message you want to send\n";

open my $mail, '|-', SENDMAIL, $to or die "Couldn't spawn sendmail: $!\n";

print $mail <<EOD;
From: $from
To: $to
Subject: $subject

$body
EOD

close $mail or die "Couldn't close pipe: $!\n";