Task:

 Generate a string with   N   opening brackets   [   and with   N   closing brackets   ],   in some arbitrary order. 
 Determine whether the generated string is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.


Examples

   (empty)      OK
   []           OK   
   [][]         OK   
   [[][]]       OK 
   ][         NOT OK
   ][][       NOT OK
   []][[]     NOT OK



sub balanced($s) {
    my $l = 0;
    for $s.comb {
        when "]" {
            --$l;
            return False if $l < 0;
        }
        when "[" {
            ++$l;
        }
    }
    return $l == 0;
}
 
my $n = prompt "Number of brackets";
my $s = (<[ ]> xx $n).flat.pick(*).join;
say "$s {balanced($s) ?? "is" !! "is not"} well-balanced"