sub traverse {
  my $element = $_[0] ;
  if (Scalar::Util::blessed ($element)) {
    if (go_ahead($element)) {
      my @contents = $element->content_list() ;
      print "Before: ", @contents, "\n\n" ;
      for my $child (@contents) {
        traverse ($child) ;
        print "Middle: ", $child, "\n\n" ;
      }
      print "After: ", @contents, "\n\n" ;
    }
  }
  else {
    print "Processing a string: " ;
    $element = curly_quotes($element) ;
    print $element, "\n\n" ;
  }
}