if ($reftype eq 'REF' || $reftype eq 'SCALAR') {
      clean($$node);
      $node = undef if !defined($$node);
   } els

##</code><code>##

sub clean {
   our $node; local *node = \$_[0];  # Alias
   return if !defined($node);

   my $reftype = ref($node);
   return if !$reftype;

   if ($reftype eq 'ARRAY') {
      clean($_) for @$node;
      @$node = grep defined, @$node;
      $node = undef if !@$node;
   } elsif ($reftype eq 'HASH') {
      clean($_) for values(%$node);
      delete @{$node}{ grep !defined($node->{$_}), keys(%$node) };
      $node = undef if !keys(%$node);
   }
}

##</code><code>##

[[[],[],["b"]],"a"]
[[["b"]],"a"]

[[[],[],[]],"a"]
["a"]

##</code><code>##

            my $n = scalar(keys %$ref);
            if ($n == 0) {
                  return 0;
            }
            return 1;

##</code><code>##

return keys(%$ref) ? 1 : 0;

##</code><code>##

return keys(%$ref);