start in timer%

Starts (or restarts) the timer. If the timer is already running, its alarm time is not changed.

• (send a-timer start msec just-once?) -> void
     msec : exact integer in [0, 1000000000]
     just-once? = #f : boolean

  The timer's alarm expires after msec milliseconds, at which point notify is called (on an event boundary). If just-once? is #f, the timer expires every msec milliseconds until the timer is explicitly stopped;¹¹ otherwise, the timer expires only once.