1:      1  1 CALL pred interpreter:main/2-0 (det) 
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> 10 step
Pure Prolog Interpreter.

      11:      6  3 CALL pred interpreter:consult/5-0 (det) 
mdb> vars
        1 HeadVar__1
        2 HeadVar__2
        3 HeadVar__4
mdb> print *
       HeadVar__1           		"interpreter.m"
       HeadVar__2           		[]
       HeadVar__4           		state('<<c_pointer>>')
mdb> goto 30
Consulting file `interpreter.m'...
      30:     17  9 CALL pred tree234:set2/4-1 (det) 
mdb> print *
       HeadVar__1           		two('<<c_pointer>>', "<standard input>", empty, empty)
       HeadVar__2           		'<<c_pointer>>'
       HeadVar__3           		"interpreter.m"
mdb> finish -a
      31:     17  9 THEN pred tree234:set2/4-1 (det) c2;t;
      32:     17  9 SWTC pred tree234:set2/4-1 (det) c2;t;c2;s1;
      33:     17  9 EXIT pred tree234:set2/4-1 (det) 
mdb> print *
       HeadVar__1           		two('<<c_pointer>>', "<standard input>", empty, empty)
       HeadVar__2           		'<<c_pointer>>'
       HeadVar__3           		"interpreter.m"
       HeadVar__4           		three(<<c_pointer>>, "interpreter.m", <<c_pointer>>, "<standard input>", empty, empty, empty)
mdb> 
      34:     16  8 EXIT pred tree234:set/4-1 (det) 
mdb> finish -n
This command is a no-op from this port.
mdb> 
      35:     15  7 EXIT pred map:set/4-1 (det) 
mdb> 
      36:     18  7 CALL pred io:set_stream_names/3-0 (det) 
mdb> continue
?-