This file has diary-style within texinfo.  Potential bugs here because
of the empty block skipping feature.  First, a block with no specified output: it
should fail because it does have output:
@example
>> a = 5;
>> disp('hi');     % doctest: +XFAIL
@end example

@example
>> a
a = 5
@end example

The first command below should not invoke skipping:
@example
>> x = 5;
>> y = x + 1
y = 6
@end example
