E1:     C1 CALL pred scripts.main/2-0 (det) scripts.m:21
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> step
      E2:     C2 CALL pred scripts.p/1-0 (det) scripts.m:28 (scripts.m:22)
mdb> finish
      E3:     C2 EXIT pred scripts.p/1-0 (det) scripts.m:28 (scripts.m:22)
mdb> track 1
p(type1(1, "foo"))
q(type1(1, "foo"))
Context of current question : scripts.m:33 (scripts.m:29)
Search mode                 : top down                   
The current question was chosen because the marked subterm was bound by
the unification inside the predicate scripts.q/1 (scripts.m:33). The
path to the subterm in the atom is 1.
      E4:     C3 EXIT pred scripts.q/1-0 (det) scripts.m:33 (scripts.m:29)
mdb> open 1
type1(
 1,
 "foo"
)
mdb> grep foo 1
 "foo"
mdb> continue
type1(1, "foo")