My approach: 
 
my $str2 = '[][[]'; 
my $str3 = "[[1,2,4],['words','dog'],[],[]]"; 
 
sub closedBrackets { 
  $_ = shift; 
  while( 1 ) { 
    my $index1 = rindex($_,'['); 
    my $index2 = index($_,']',$index1); 
    return 1 if ($index1 < 0 && $index2 < 0); 
    return if ($index1 > 0 && $index2 < 0) || ($index1 < 0 && $index2 > 0); 
    $_ = substr($_,0,$index1) . substr($_,$index2+1); 
  } 
} 
 
closedBrackets($str2) ? print $str2 . " ok\n" : print $str2 . " NOT ok\n"; 
closedBrackets($str3) ? print $str3 . " ok\n" : print $str3 . " NOT ok\n";

[]][

my $str = '[helow [] ] []'; 
 
sub isBalanced { 
  my $balanced = 0; 
  for (split(//,shift)) { 
    $balanced++ if /\[/; 
    $balanced-- if /\]/; 
    return if $balanced < 0; 
  } 
  $balanced == 0 ? return 1 : return; 
} 
 
 
print "Balanced\n" if isBalanced($str); 
print "Not Balanced\n" if not isBalanced($str);

I have a string s = '[[][]]' 
 
How would I go about making sure all the brackets are closed 'properly' 
 
Something like '[[][[[]' is not considered closed properly