perldoc XML::Twig says:
- keep_encoding
-
This is a (slightly?) evil option: if the XML document is not
UTF-8 encoded and you want to keep it that way, then setting
keep_encoding will use the"Expat" original_string method for
character, thus keeping the original encoding, as well as the
original entities in the strings
s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e