E1:     C1 CALL pred exception_cmd.main/2-0 (det) exception_cmd.m:17
mdb> echo on
Command echo enabled.
mdb> exception
      E2:     C2 EXCP pred exception_cmd.test/2-0 (det)
mdb> print *
       X (arg 1)              	42
mdb> continue
Uncaught Mercury exception:
Software Error: oops
Last trace event was event #E3.
Last trace event before the unhandled exception was event #E4.