You have not declared the variable, $_second_octet_num variable. I don't know how your program is generating 192.168.1.1 to 192.168.1.254 without that.

Here I am giving the code for generating a IP address from 192.168.1.1 to 192.168.254.254. You can adjust the code according to your situation.

#!/usr/bin/perl
use strict;
use warnings;

my $first_octet_num = "1";
my $ip_address;

foreach (1..254) {
    foreach (1..255) {
        if ($_ <= 254) {
            $ip_address = join ('.', 192,168,$first_octet_num,$_);
            print "$ip_address\n";
        } else {
            $first_octet_num++;
        }
    }
}
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One more information for you, IP address start with 192, it's not class B. It's class C. Reference here.