my $foo = [
  1,
  [2, 3],
  [4, [5, 6, 7]],
];

my $path = Thing->new($foo);
while( defined( my $p = $path->next )) {
    print join( ' ' => @$p ), "\n";
}

__PRDDUCES__

1 2 4 5
1 2 4 6
1 2 4 7
1 3 4 5
1 3 4 6
1 3 4 7