The third subroutine is handle_exceptions. It is invoked if a Perl exception is caught by a MIC-compliant piledriver.6.1 If an exception is thrown, then it will be handed off to handle_exceptions().6.2 Whatever this page returns will be handed off to the customer. Therefore, handle_exception should generally retun a nice HTML page reporting the error.
Since MIC provides robust error handling for field related errors, this type of error reporting should generally be reserved for errors that ``shouldn't happen.'' Of course, this doesn't mean that the error shouldn't look nice.