use HTML::TokeParser::Simple;
  use HTML::Tagset;

  my $p = HTML::TokeParser::Simple->new( \$html );

  while ( my $token = $p->get_token ) {
     next if $token->is_tag
              and
              exists $HTML::Tagset::isKnown{ $token->return_tag };
     print $token->return_text;
  }