All values should be undefined:
global value: $a = global value
$a =
lokal value: $a = lokal value
again global value: $a = global value
0 = 1
0
1 = 4
0
1
2 = 8
0
1
2
3 = 17
0
1
2
3
| 0 | b1/1 | ||||
| 1 | b2/1 | 1 | b2/2 | ||
| 2 | b3/1 | 2 | b3/2 | 2 | b3/3 |