in reply to truncating form field input to 4000 characters

Line breaks may be a reason and also UTF-8 characters as they are composed of 2 or more bytes.

s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e