That's correct. I'm guessing either you cannot actually retrieve the dtd or you're getting some invalid cached copy of the dtd. If you really want to validate, you can load it from a file (rather then let libxml retrieve it via a network call) and then pass the string to the Dtd constructor:

  local $/ = undef;
  open my $fh, "<", $file || die "cannot open $file - $!\n";
  my $str = <$fh>;
  close $fh;
  
  my $dtd = XML::LibXML::Dtd->parse_string( $str );
[download]