(c) : continue execution (more accurately, post to the continue semaphore)
(events) : show all debugging events
(e #) : pick which event to examine

... the following are all implicitly parameterized
    by the chosen event:

  (bt) : summarize the continuation
  (f #) : examine the #th frame of the continuation

  ... the following are all implicitly parameterized
      by the chosen frame
    (bound) : all bound vars
    (v <x>) : value of a named variable
    (src) : the source code