Re: replacing the last portions of an octet

[atcroft]

Here were two functions I wrote (before I found out about things like Net::IP or NetAddr::IP that you might find helpful:

sub dq2number { 
    my $ip = shift; 
    return unpack "N", pack "C4", split /\D/, $ip; 
} 
sub number2dq { 
    my $n = shift; 
    return join q{.}, unpack "C4", pack "N", $n; 
}

Here is an example, so you can see the result

use strict;
use warnings;

my @c = qw/
  0.0.0.0  
  0.255.255.255 
  10.0.0.1 
  172.16.0.1 
  127.0.0.1 
  192.168.0.1
  /; 
foreach my $d (@c) { 
    print $d, q{ }, 
      number2dq( dq2number( $d ) - 1 ), q{ }, 
      number2dq( dq2number( $d ) + 1 ), qq{\n}; 
}
sub dq2number { 
    my $ip = shift; 
    return unpack "N", pack "C4", split /\D/, $ip; 
} 
sub number2dq { 
    my $n = shift; 
    return join q{.}, unpack "C4", pack "N", $n; 
}
# Output:
# 0.0.0.0 255.255.255.255 0.0.0.1
# 0.255.255.255 0.255.255.254 1.0.0.0
# 10.0.0.1 10.0.0.0 10.0.0.2
# 172.16.0.1 172.16.0.0 172.16.0.2
# 127.0.0.1 127.0.0.0 127.0.0.2
# 192.168.0.1 192.168.0.0 192.168.0.2

Hope that helps.