static Var<OKOrError<S>> backtickInNewThread(fS cmd) {
  final new Var<OKOrError<S>> var;
  startThread("`" + cmd, r {
    try {
      var.set(OKOrError_ok(backtick(cmd)));
    } catch e {
      printStackTrace(e);
      var.set(OKOrError_error(e));
    }
  });
  ret var;
}