1:      1  1 CALL pred exception_vars.main/2-0 (det) exception_vars.m:12
mdb> echo on
Command echo enabled.
mdb> goto 2
       2:      2  2 CALL pred exception_vars.test/2-0 (det) exception_vars.m:19 (exception_vars.m:12)
mdb> finish
       6:      2  2 EXCP pred exception_vars.test/2-0 (det)
mdb> print *
       X (arg 1)              	42
mdb> continue
Uncaught Mercury exception:
Software Error: oops
Last trace event was event #9.
Last trace event before the unhandled exception was event #4.