use strict;

my @block  = qw/ 1 2 3 4 5 6 7 8 9 /;
my $target = 20;

my @solutions = solve($target,@block);
print join(',',@$_) . "\n" for ( @solutions );

# find all combinations of blocks that sum to target
sub solve {
    my ( $target, @block ) = @_;
    my ( @solutions, @trial, @stack );
    my $acc = -1;

  NEW: while (1) {
        if ( sum( \@trial ) == $target ) {
            my @solu = @trial;
            push @solutions, \@solu;
        }
      OLD: while (1) {
            $acc++;
            if ( $acc <= $#block ) {
                push @trial, $block[$acc];
                push @stack, $acc;
                next NEW;
            }
            elsif (@stack) {
                pop @trial;
                $acc = pop @stack;
                next OLD;
            }
            else { last NEW }
        }
    }

    return @solutions;
}

sub sum {
    local $_;
    my ($array) = @_;
    my $sum;
    $sum += $_ for (@$array);
    return $sum;
}