If instead we wanted to register an arbitrary subroutine (defined using sub method_name{ ... }), we would have to register a reference to this subroutine like so: -command=>\&method_name.
如果不采用这种方法的话，我们要想注册一个子例程（用 sub method_name{ ... } 来定义），那么必须注册一个到这个子例程的引用，类似于： -command=>\&method_name 。
2
Including the main program, sub-control robot moves, voice and speech recognition to play subroutine program.