static TimedCache<S> adbForward_list = new TimedCache(10);

static void adbForward() {
  if (!isOnPATH("adb"))
    print("adb not on path");
  else {
    backtick_verbose = true;
    S list = adbForward_list.get(new O() { O get() { ret backtick("adb forward --list"); }});
    if (!contains(list, "4995"))
      backtick("adb forward tcp:4995 tcp:4999");
  }
}

Began life as a copy of #1004458