Select Code to Download

use strict;
use warnings;
...
.
10.20.255.253
10.20.255.254

sub parse_ipv4 {
   local *_ = \(@_ ? $_[0] : $_);
...

   return unpack('N', pack('C4', $1, $2, $3, $4));
}

    Mask            Number of addresses printed
/32 255.255.255.255 0
...
/2  192.0.0.0       1,073,741,822
/1  128.0.0.0       2,147,483,646
/0  0.0.0.0         4,294,967,294