Hi Uwe,

On 21/04/2009, at 8:30 PM, Uwe Lück wrote:

> I wonder whether this is a bug that should go to the LaTeX Bug  
> Database, since it only
> -- is about an internal
> -- contradicts what one might expect
> -- while it is not clear to me whether this can affect LaTeX's  
> function on the user-level

This certainly seems like a bug to me, although I had to modify your  
examples to see the error:
	\in@{bonbon}{bon}\ifin@ YES\else NO\fi  % gives YES
	\in@{bonbon}{bonb}\ifin@ YES\else NO\fi % gives NO
	\in@{client-to-client}{client-to}\ifin@ YES\else NO\fi  % gives NO
	\in@{client-to-client}{client-to-}\ifin@ YES\else NO\fi % gives YES
The tendency seems to be not to change the internals of LaTeX2e, but  
I'd be happy to replace the current implementation of \in@ with a more  
correct version. What do others think? If others are amenable to the  
change, would you be willing to write the new version?