use strict;

my %exception_second_octet = map {$_=> "Put Subclass Info here"} qw( 6  17  19);

for my $second_octet (1..23){
    if ($exception_second_octet{$second_octet}){
        # Put Subclass generation code here
    } else {
        for my $fourth_octet(1..255){
           my $generated_ip = "10.$second_octet.0.$fourth_octet/32";
           # Do whatever else ...
        }
    }
}