svoid closeAllOpt(Iterable l) {
  if (l == null) ret;
  for (O c : l)
    pcall { if (c cast AutoCloseable) close(c); }
}

svoid closeAllOpt(O... l) {
  if (l == null) ret;
  for (O c : l)
    pcall { if (c cast AutoCloseable) close(c); }
}