$host = "ip_or_hostname_to_check_here";
$name_of_comp_to_notify = 'computer66';

print "Started ...\n";
&ping_check;

sub ping_check {

    &current_date_time;

    use Net::Ping;
    $p = Net::Ping->new("icmp");

    if ($p->ping($host, 2)) {
        &host_up;
    } else {
        &host_down;
    }

    $p->close();
}

sub host_up {
    print "$date_time - Host $host is up\n";
    system("net send $name_of_comp_to_notify $host is up");
}

sub host_down {
    print "$date_time - Host $host is down\n";
    sleep 30;
    &ping_check;
}

sub current_date_time {
    ($sec,$min,$hr,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);
    $longyr = $year + 1900;
    $fixmo = $mon + 1;
	
    if ($mday < 10)  { $mday = "0$mday"   ; }
    if ($fixmo < 10) { $fixmo = "0$fixmo" ; }
    if ($hr < 10)    { $hr = "0$hr"       ; }
    if ($min < 10)   { $min = "0$min"     ; }
    if ($sec < 10)   { $sec = "0$sec"     ; }

    $date_time="$mday\/$fixmo\/$longyr  $hr:$min:$sec";
}