* reverse-continue ('rc') -- Continue program being debugged but run it in reverse
* reverse-finish -- Execute backward until just before the selected stack frame is called
* reverse-next ('rn') -- Step program backward, proceeding through subroutine calls.
* reverse-nexti ('rni') -- Step backward one instruction, but proceed through called subroutines.
* reverse-step ('rs') -- Step program backward until it reaches the beginning of a previous source line
* reverse-stepi -- Step backward exactly one instruction
* set exec-direction (forward/reverse) -- Set direction of execution.