my @res = (2, 2, 2, 5, 5, 5);
my $goal = 1000;

print closest($goal, \@res), "\n";

sub closest{
    my $exact = shift;
    my $array = shift;

    my $best = 0;

    for my $n ( get_numbers($array) ){
        $best = $n if abs( $exact - $n**2) < abs( $exact - $best**2);
    }
    $best;
}

sub get_numbers{
    my $array = shift;

    my $length = @$array;

    if ($length == 1){
        return ( $array->[0] );
    }
    else{
        my @ret_arr;
        my $n = shift @$array;
        push @ret_arr, $n;
        my @tmp = get_numbers($array);
        push @ret_arr, @tmp;
        push @ret_arr, $n*$_ for @tmp;
        prune(@ret_arr);
    }
}

sub prune{
    my %h;

    undef $h{$_} for @_;
    keys %h;
}