#!/usr/bin/env perl -l

use strict;
use warnings;

use List::Util qw{sum};

my @test_arrays = ( 
    [1, 3, 8, 4], 
    [1, 6, 2], 
    [1, 3, 5, 7], 
    [4, 3, 2, 2, 1],
    [4, 3, 2, 2, 2, 2, 1],
    [5, 5, 4, 6, 2, 8, 1, 9],
);  

check_arrays($_) for @test_arrays;

sub check_arrays {
    my @full_array = @{shift()};
    print "Checking: (", join(", " => @full_array), ")";
    my $sum = sum @full_array;

    if ($sum % 2) {
        print "\tSubsets not equal";
        return;
    }   

    my $half = $sum / 2;
    my (@a1, @a2);

    for (sort { $b <=> $a } @full_array) {
        push @{(sum(@a1) || 0) + $_ <= $half ? \@a1 : \@a2} => $_;
    }

    print "\tSubsets: (", join(", " => sort { $a <=> $b } @a1),
            ") and (", join(", " => sort { $a <=> $b } @a2), ")";
    print "\tSubset sum = $half";
}