s[
    (?: <!--.*?-->                                   ) |
    (?: <[?!].*?>                                    ) |
    (?: <([a-z0-9]+)\b((?:[^>'"]|"[^"]*"|'[^']*')*)> ) |
    (?: </([a-z0-9]+)>                               ) |
    (?: (.[^<]*)                                     )
  ][
    defined $1 ? cleanup_tag(lc $1, $2)              :
    defined $3 ? cleanup_close(lc $3)                :
    defined $4 ? cleanup_cdata($4)                   :
    ''
  ]igesx;