- spy(Spec)
- Hook in spy/1. If the hook succeeds spy/1 takes no further action.
- nospy(Spec)
- Hook in nospy/1. If the hook succeeds nospy/1 takes no further action. If spy/1 is hooked, it is advised to place a complementary hook for nospy/1.
- nospyall
- Hook in nospyall/0. Should remove all spy points. This hook is called in a failure-driven loop.
- debugging
- Hook in debugging/0. It can be used in two ways. It can report the status of the additional debug points controlled by the above hooks and fail to let the system report the others, or it succeeds, overruling the entire behaviour of debugging/0.