All values should be undefined:
[* $a = 'global value' ; *] 
global value: $a = [+ $a || ''  +] 
[* { local $a ; *]
$a = [+ $a || ''  +] 
[* $a = 'lokal value' ; *] 
lokal value: $a = [+ $a || ''  +] 
[* } *]
again global value: $a = [+ $a || ''  +] 
[* @x = (1, 4 ,8, 17) ; *]
[- $i = 0 -]
[$ while $i <= $#x $]
    [+ $i +] = [+ $x[$i] +] 
    [* $j = 0 ; *]
    [$ while $j <= $i $]
        [+ $j++ +] 
    [$ endwhile $]
    
    [* $i++ ; *]
[$ endwhile $]
[-
   undef @b ;
   $b[0][0] = 'b1/1' ;
   $b[1][0] = 'b2/1' ;
   $b[1][1] = 'b2/2' ;
   $b[2][0] = 'b3/1' ;
   $b[2][1] = 'b3/2' ;
   $b[2][2] = 'b3/3' ;
-]
| [* $i = $row ; *][+ $i +] | [+ $b[$row][$col] +] |