In the event of a restricted environment where non-core modules are banned, here's a way to do it using only the core Socket module.

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( $binMa
+sk ),
   q{Network},
      unpack( q{(a8)*}, unpack( q{B*}, $network ) ), $hrNetwork,
   q{Low address},
      unpack( q{(a8)*}, unpack( q{B*}, $lowAddr ) ), inet_ntoa( $lowAd
+dr ),
   q{High address},
      unpack( q{(a8)*}, unpack( q{B*}, $highAddr ) ), inet_ntoa( $high
+Addr );

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

The full output running with a 27-bit mask.

johngg@shiraz:~/perl/Monks > ./spw1174132 1.2.3.4/27

IP address   : 00000001 00000010 00000011 00000100 : 1.2.3.4
Netmask      : 11111111 11111111 11111111 11100000 : 255.255.255.224
Network      : 00000001 00000010 00000011 00000000 : 1.2.3.0/27
Low address  : 00000001 00000010 00000011 00000001 : 1.2.3.1
High address : 00000001 00000010 00000011 00011111 : 1.2.3.31

Address range
     1.2.3.1
     1.2.3.2
     1.2.3.3
     1.2.3.4
     1.2.3.5
     1.2.3.6
     1.2.3.7
     1.2.3.8
     1.2.3.9
     1.2.3.10
     1.2.3.11
     1.2.3.12
     1.2.3.13
     1.2.3.14
     1.2.3.15
     1.2.3.16
     1.2.3.17
     1.2.3.18
     1.2.3.19
     1.2.3.20
     1.2.3.21
     1.2.3.22
     1.2.3.23
     1.2.3.24
     1.2.3.25
     1.2.3.26
     1.2.3.27
     1.2.3.28
     1.2.3.29
     1.2.3.30
     1.2.3.31
[download]

Head and tail of a run with an 18-bit mask.

johngg@shiraz:~/perl/Monks > ./spw1174132 1.2.3.4/18

IP address   : 00000001 00000010 00000011 00000100 : 1.2.3.4
Netmask      : 11111111 11111111 11000000 00000000 : 255.255.192.0
Network      : 00000001 00000010 00000000 00000000 : 1.2.0.0/18
Low address  : 00000001 00000010 00000000 00000001 : 1.2.0.1
High address : 00000001 00000010 00111111 11111111 : 1.2.63.255

Address range
     1.2.0.1
     1.2.0.2
     1.2.0.3
     1.2.0.4
     1.2.0.5
     1.2.0.6
     1.2.0.7
     1.2.0.8
     1.2.0.9
     1.2.0.10
     1.2.0.11
     1.2.0.12
     1.2.0.13
     1.2.0.14
     1.2.0.15
     1.2.0.16
     1.2.0.17
...
     1.2.63.241
     1.2.63.242
     1.2.63.243
     1.2.63.244
     1.2.63.245
     1.2.63.246
     1.2.63.247
     1.2.63.248
     1.2.63.249
     1.2.63.250
     1.2.63.251
     1.2.63.252
     1.2.63.253
     1.2.63.254
     1.2.63.255
[download]

I hope this is of interest.

Update: Fixed typo and condensed the address range code slightly.

Update 2: Fixed line above which was garbled for some reason.