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 |