Hello Anonymous Monk,

For some reason, none of the solutions below wanted to work within my script.. Can you try this one, if it is working?

It is really strange that you need to do this much work, read and write to a file for IP manipulations.

#!/usr/bin/env perl
use strict;
use warnings;
use NetAddr::IP;
use feature 'say';

my $final;
my $input = '127.0.0.3';

my @ip = split /\./, $input;

if ($ip[3] % 2) {
    $final = join '.', @ip;
    $final = NetAddr::IP->new($final.'/8') + 1;
}
else {
    $final = join '.', @ip;
    $final = NetAddr::IP->new($final.'/8') - 1;
}

$final = substr $final, 0, -2;
say $final;

__END__

$ perl test.pl
127.0.0.4
[download]

BR / Thanos