@ary = map { pack "B32", join "", (1) x $_, (0) x (32 - $_) } 0..31;
$dotted    = "192.168.248.17";
$netmask   = $ary[19]; # prefix 19, i.e. cidr 192.168.248.17/19
$address   = pack "C4", split /\./, $dotted;
$network   = $address & $netmask;
$broadcast = $address | ~ $netmask;
print $_,$/ 
  for map {
    join ".", unpack "C4", $_
  } $netmask, $address, $network, $broadcast;
__END__
255.255.224.0
192.168.248.17
192.168.224.0
192.168.255.255