Turns on the debugger in 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
leash/1). 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 Execution).