E1:     C1 CALL pred user_event_2.main/2-0 (det) user_event_2.m:14
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> user
      E2:     C2 USER <event_with_zero_arity_defined_type> pred user_event_2.do_something/3-0 (det) c1; user_event_2.m:20
mdb> print *
       arg (attr 0, Data)     	foo(43)
mdb> continue