- called for each error with the object name as $_[0], the method name
- as $_[1], the current file as $_[2] and the line number as $_[3].
+ called for each error with a string representation of the object as
+ $_[0], the method name as $_[1], the current file as $_[2] and the
+ line number as $_[3]. If and only if the object is actually a block,
+ $_[0] is assured to start by '{'.