Prev: error
error_arg()This function, which you should only call inside an error handler for a catch statement (see Error-Handling Statements), returns the error argument specified in the
throw() call which caused the error
which triggered the error handler, or 0 if the no error argument
was specified in the throw() caller or if the error was thrown by
the interpreter. If you are not in an error handler, this function
throws an ~error error.