    **/
    CImg<T>& operator^=(const char *const expression) {
      return *this^=(+*this)._fill(expression,true,1,0,0,"operator^=",this);
    **/
    CImg<T>& operator^=(const char *const expression) {
      return *this^=(+*this)._fill(expression,true,1,0,0,"operator^=",this);