use strict;
use warnings;

use feature qw{ say };

use Socket;

my $ipAddr = shift;
my( $quad, $mask ) = split m{/}, $ipAddr;

die qq{Bad IP\n} unless my $binAddr = inet_aton( $quad );

my $rxValidMask = do {
   local $" = q{|};
   my @vals = ( 8 .. 30 );
   qr{^(?:@vals)$};
   };
die qq{Bad mask\n} unless $mask =~ $rxValidMask;

my $value   = 0xffffffff;
$value      = do {
   no warnings qw{ portable };
   ( $value <<= 1 ) % 0x100000000;
   } for 1 .. ( 32 - $mask );
my $binMask = pack q{N}, $value;

my $network = $binAddr & $binMask;

my $lowMask = $network ^ pack q{H*}, q{00000001};
my $lowAddr = $network | $lowMask;

my $highMask = $binMask ^ pack q{H*}, q{ffffffff};
my $highAddr = $network | $highMask;

my $hrNetwork
   = inet_ntoa( $network )
   . q{/}
   . ( unpack( q{B*}, $binMask ) =~ tr{1}{} );

print qq{\n};
my $lineFmt = qq{%-13s: %s %s %s %s : %s\n};
printf
   $lineFmt x 5,
   q{IP address},
      unpack( q{(a8)*}, unpack( q{B*}, $binAddr ) ), $quad,
   q{Netmask},
      unpack( q{(a8)*}, unpack( q{B*}, $binMask ) ), inet_ntoa( $binMask ),
   q{Network},
      unpack( q{(a8)*}, unpack( q{B*}, $network ) ), $hrNetwork,
   q{Low address},
      unpack( q{(a8)*}, unpack( q{B*}, $lowAddr ) ), inet_ntoa( $lowAddr ),
   q{High address},
      unpack( q{(a8)*}, unpack( q{B*}, $highAddr ) ), inet_ntoa( $highAddr );

print qq{\nAddress range\n};
do {
   say q{     }, inet_ntoa( $lowAddr );
   $lowAddr = pack q{N}, 1 + ( unpack q{N}, $lowAddr );
   } while $lowAddr le $highAddr;