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