while(  $html !~ m#\G$#gc  ) {
    if(  $html =~ m#\G([^&<]+)#gc  ) {
        # $1 is plain text
    } elsif(  $html =~ m#\G<!--(.*?)-->#gc  ) {
        # $1 is a comment
        # I think HTML comments are defined by the standard
        # to actually be more complex than that, but the
        # practical definition appears to match the above.
    } elsif(  $html =~ m#\G<((?:[^"'>]+|"[^"]*"|'[^']*')*)>#gc  ) {
        # $1 is the inside of a tag
    } elsif(  $html =~ m#\G&(\w+);#gc  ) {
        # $1 is the name of an entity
    } elsif(  $html =~ m!\G&#(\w+);!gc  ) {
        # $1 is the number of an entity
    } else {
        # We have hit invalid HTML.
        # You can try to be lenient here if you like:
        if(  $html =~ m#\G([&<])#gc  ) {
            # Treat like a &amp; or &lt; if you like
        } else {
            die "Impossible??";
        }
    }
}