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";