catch (Throwable t) { rethrow(t);
catch (RuntimeException e) { rethrow(e, RuntimeException.class);
  public Value execute(Env env)    throws Throwable  {    try {      do {        env.checkTimeout();        Value value = _block.execute(env);        if (value == null) {        }        else if (value == BreakValue.BREAK)          return null;        else if (value == ContinueValue.CONTINUE) {        }        else          return value;      } while (_test.evalBoolean(env));    }    catch (Throwable t) {      rethrow(t);    }    return null;  }