Put the first breakpoint inside the error() function in the case where it prints an error message. This breakpoint will be a line breakpoint on line 33.
In a larger program, you can easily change the current function in the Editor window by typing the following, for example, in the Debugger Console window:
(dbx) func error
The lavender stripe indicates the match found by the func command.
Create the line breakpoint by clicking in the left margin of the Editor window on top of the number 33.
Click Restart to run the program and upon hitting the breakpoint, the stack trace shows the error message that is generated due to the simulated command in the in file:
> display var # should yield an error
The call to error() is expected behavior.
Click Continue to continue the process and hit the breakpoint again.
An unexpected error message appears.