XEmacs 21.4.12:
The errors thrown by `scan-lists' is of type `error' whereas I
expected them to be of some more specific subclass like
`syntax-error'.
Test case: Start xemacs -q -no-site-file. Evaluate
(condition-case nil (scan-lists 0 -1 -1) (syntax-error nil))
I expected this to return nil, but it throws an error.