Turns the debugger on and starts it creeping; that is, it sets the debugger to trace mode.
The debugger will start showing goals as soon as the first call
is reached, and it will stop to allow you to interact as
soon as it reaches a leashed port (see
mpg-ref-leash). Setting the debugger to trace mode means
that every time you type a query, the debugger will start by creeping.
The effect of this predicate can also be achieved by typing the letter t after a ^c interrupt (see ref-iex-int).
This predicate is not supported in runtime systems.