Specification Details

12. Exception Handling and Debugging

[Disagreement with ANS]

If the line number is omitted, the value of EXLINE is 0.
If an exit-do or exit-for statement is executed in the exception-handler of a when-use-block that is contained in a do-block or for-block, the control escapes from the exception handler. (ANS does not mention this.)
When an exception is caused by a statement lexically within an exception-handler, this exception is handled as an ordinary exception.
12.1.6 Remarks
When an exception occurs within a def-statement, this system obeys the rule in 12.1.4. (The description in ANS is probably incorrect.)
Results of a trace-statement may slightly differ from the standard, in particular, even if an assign-statement is executed, no report shall be outputted if the value of the variable is not changed.
Only array elements that are changed in values are reported.

On the description at 12.1.4
"A separate GOSUB stack is associated with each exception-handler (cf. 8.2) ... ",
"exception-handler" seems to be a mistake for "detached-handler".