static L<S> splitCamelCasePlusUnderscores(S s) {
  int j = 0;
  new L<S> l;
  
  // new addition
  if (isAllUpperCase(s)) ret l with l.add(s);
  
  for i over s: {
    char last = charAt(s, i-1), c = s.charAt(i);
    if (i > j && (isUpperCaseLetter(c) || last == '_' || c == '_')) {
      l.add(substring(s, j, i));
      j = i;
    }
  }
  if (j < l(s))
    l.add(substring(s, j));
  ret l;
}

Began life as a copy of #1012527