static L<S> tok_joinEllipsis_flex(L<S> tok) {
  for (int i = 1; i+4 < l(tok); i += 2)
    if (allEq(".", get(tok, i), get(tok, i+2), get(tok, i+4))) {
      removeSubList(tok, i+1, i+5);
      tok.set(i, "...");
    }
  ret tok;
}