#!/usr/bin/perl

$curr_day = int time / (3600 * 24);
open SHADOW, "/etc/shadow";
while (<SHADOW>) {
    @entry = split ':';
    if ($entry[2] + $entry[4] - $curr_day == 5) {
	open MAIL, "|mail $entry[0]";
	print MAIL "Your password will expire in five days.\n";
	print MAIL "Please change it as soon as possible.\n";
	close MAIL;
    }
}