I'm not 100% sure, since this module is a parser and not a serializer, but it appears HTML::HTML5::Parser is just building a DOM, and the serialization is then done by XML::LibXML. Therefore, it seems likely the bug is indeed in HTML::HTML5::Parser.
The upstream bug tracker is at https://rt.cpan.org/Public/Dist/Display.html?Name=HTML-HTML5-Parser but unfortunately, it doesn't see a lot of attention these days. Nevertheless, please submit upstream.
I'm not 100% sure, since this module is a parser and not a serializer, but it appears HTML::HTML5::Parser is just building a DOM, and the serialization is then done by XML::LibXML. Therefore, it seems likely the bug is indeed in HTML::HTML5: :Parser.
The upstream bug tracker is at /rt.cpan. org/Public/ Dist/Display. html?Name= HTML-HTML5- Parser
https:/
but unfortunately, it doesn't see a lot of attention these days. Nevertheless, please submit upstream.