sub my_inet_aton {
  my ($string) = @_;
  my ($a, $b, $c, $d) = split(/\./, $string);

  return ( ($a << 24) +
           ($b << 16) +
           ($c << 8)  +
           ($d) );
}

sub my_inet_ntoa {
  my ($ip) = @_;

  return ( (($ip & 0xFF000000) >> 24) . '.' .
           (($ip & 0xFF0000) >> 16)   . '.' .
           (($ip & 0xFF00) >> 8)      . '.' .
             ($ip & 0xFF) );
}

##</code><code>##

my $ipstring   = '192.168.190.128';
my $maskstring = '255.255.255.0';

my $ip   = my_inet_aton($ipstring);
my $mask = my_inet_aton($maskstring);

my $subnet = $ip & $mask;

print "Subnet portion of ", $ipstring, "/", $maskstring,
      " is ", my_inet_ntoa($subnet), "\n";