Mr Zesty's Brain Dump: Service Greeting scan

Service Greeting scan

I use this script to scan a subnet and find the response on a given port - both to check how quiet the service is, and to see what version it is.
#!/usr/bin/perl
 
# If they tried to use anything but 3 arguments - show them the
# usage instructions
if ($#ARGV + 1 > 0 && $#ARGV + 1 != 3) {
  print "Usage: $0 <start> <end> <port>\n\n";
  exit(1);
}
 
# Check for something that looks like an IP address, or prompt for one
until (@ARGV[0] =~ /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/) {
  print "Enter the starting IP [192.168.0.1]: ";
  $start=<STDIN>;
  chomp $start;
  if(! $start) { $start="192.168.0.1"; }
  @ARGV[0]=$start;
}
 
# Get a number for the IP to stop at
until (@ARGV[1] =~ /^\d{1,3}$/) {
  print "Enter the ending IP [254]: ";
  $end=<STDIN>;
  chomp $end;
  if(! $end) { $end=254; }
  @ARGV[1]=$end;
}
 
# Get a port number to scan on
until (@ARGV[2] =~ /^\d+$/) {
  print "Enter the Port number to scan [80]: ";
  $port=<STDIN>;
  chomp $port;
  if(! $port) { $port=80; }
  @ARGV[2]=$port;
}
 
print "Scanning Port #@ARGV[2], from @ARGV[0] to @ARGV[1]\n";

# We need to get the last octet of the start IP somehow...
@class=split(/\./,@ARGV[0]);
 
use Socket;
 
$a=@class[3];
 
while ($a < @ARGV[1]) {
 
        socket(SH, PF_INET, SOCK_STREAM, getprotobyname('tcp')) || die $!;
 
        $ip="@class[0].@class[1].@class[2].${a}";
 
        my $dest = sockaddr_in (@ARGV[2], inet_aton("${ip}"));
 
        print "$ip\n";
 
        if(system("ping -c1 $ip >/dev/null")) {
                print "Host not pingable\n\n";
        } else {
                # If we're scanning port 80 we can just use lynx
                if(@ARGV[2] eq 80) {
                        system("lynx -dump -head http://$ip");
                } else {
                # Otherwise proceed with opening a socket and reading the output
                        if (connect (SH, $dest)) {
                                $buffer = <SH>;
                                shutdown (SH,0) || die $!;
                                print "$buffer\n";
                        } else {
                                print "$!\n\n";
                        }
                }
        }
        # Move to the next IP
        $a++;
}