-  spy(:Spec) is det
 
-  nospy(:Spec) is det
 
-  nospyall is det
 - Set/clear spy-points. A successfully set or cleared spy-point is
reported using print_message/2, level 
informational, with one of
the following terms, where Spec is of the form M:Head.
- See also
 - - spy/1 and nospy/1 call the hook prolog:debug_control_hook/1
to allow for alternative specifications of the thing to
debug.