static S replacePartBetweenStrings(S s, S begin, S end, S replacement) {
  if (s == null) null;
  int i = indexOf(s, begin);
  if (i < 0) ret s;
  i += l(begin);
  int j = indexOf(s, i, end);
  if (j < 0) ret s;
  ret substring(s, 0, i) + replacement + substring(s, j);
}