cat1
	cat1,sub1
		cat1,sub1,sub-sub1
	cat1,sub2
cat2
cat3
	cat3,sub1

##</code><code>##

------------------------------------
| id | name               | parent |
------------------------------------
| 1  | cat1               | 0      |
| 2  | cat1,sub1          | 1      |
| 3  | cat1,sub1,sub-sub1 | 2      |
| 4  | cat1,sub2          | 1      |
| 5  | cat2               | 0      |
| 6  | cat3               | 0      |
| 7  | cat3,sub1          | 6      |
------------------------------------

##</code><code>##

my @x =
('cat1',
  ['cat1,sub1',
    ['cat1,sub1,sub-sub1'],
   'cat1,sub2'],
 'cat2',
 'cat3',
  ['cat3,sub1'],
);

##</code><code>##

$x[0] is SCALAR	1/0 (id/parent)
$x[1] is ARRAY
$x[1][0] is SCALAR	2/1
$x[1][1] is ARRAY
$x[1][1][0] is SCALAR	3/2
$x[1][1][1] isn't defined
$x[1][2] is SCALAR	4/1
$x[1][3] isn't defined
$x[2] is SCALAR	5/0
$x[3] is SCALAR	6/0
$x[4] is ARRAY
$x[4][0] is SCALAR	7/6
$x[4][1] isn't defined
$x[5] isn't defined