#! C:\perl\bin\perl.exe

use strict;
use warnings;

print checksum('000181080002020202020202');

sub checksum {
	my $region = shift;
	$region =~ s/(\w{2})(?!$)/$1,/g;
	my @region_array = split(/,/, $region);
	my $total = 0;
	foreach(@region_array){
		$total += hex($_);
	}
	print "Total decimal: $total\n";
	my $total_hex = sprintf('%X', $total);
	print "Total Hex: $total_hex\n";
	my ($lsb) = $total_hex =~ /([a-zA-Z0-9]{2}$)/;
	print "LSB: $lsb\n";
	my $cs_bin = $lsb ^ 0xff;
	my $cs_int = sprintf('%d', $cs_bin);
	print "CS Decimal: $cs_int\n";
	my $cs_hex = sprintf('%X', $cs_int);
	return $cs_hex;
}