Halting on a PL/I line only if a condition is true
Often a particular part of your program works fine for the first
few thousand times, but it fails under certain conditions. You don't
want to just set a line breakpoint because you will have to keep entering GO.
Example: sample PL/I program for debugging
For example, in PLICALC you want to stop at the division
selection only if the divisor is 0 (before the exception occurs).
Set the breakpoint like this:
AT 31 DO; IF NUM ^= 0 THEN GO; END;