use warnings;
use strict;
use Math::Prime::Util::GMP qw/sigma/;
use Path::Class qw/file/;
#OR: use Storable qw/store retrieve/;

my $cache_file = '/tmp/abundant_sums_cache';
my @arr_sum_two_abundant_numbers;
if (-e $cache_file) {
	@arr_sum_two_abundant_numbers = file($cache_file)->slurp(chomp=>1);
	#OR: @arr_sum_two_abundant_numbers = @{ retrieve($cache_file) };
}
if (!@arr_sum_two_abundant_numbers) {
	print "regenerating \@arr_sum_two_abundant_numbers...\n";
	my @arr_abundant = grep { sigma($_)>2*$_ } 12 .. 28123;
	my %hash;
	foreach my $i (@arr_abundant) {
		foreach my $j (@arr_abundant) {
			my $positive = $i + $j;
			next if $positive > 28123;
			$hash{$positive}++;
		}
	}
	@arr_sum_two_abundant_numbers = sort {$a <=> $b} keys %hash;
	file($cache_file)->spew_lines(\@arr_sum_two_abundant_numbers);
	#OR: store(\@arr_sum_two_abundant_numbers, $cache_file);
}
else { print "loaded \@arr_sum_two_abundant_numbers from $cache_file\n" }

my $sum_total;
my $n = 1;
foreach my $key (@arr_sum_two_abundant_numbers) {
	for ( my $i=$n ; $i < $key ; $i++) {
		$sum_total += $i;
	}
	$n = $key +1;
}
print "$sum_total\n";