Dear LaTeX, 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 What do you expect from \in@{ionization}{ionizat}\typeout{\ifin@ YES\else NO\fi} or \in@{bonbon}{bon}\typeout{\ifin@ YES\else NO\fi} or \in@{client-to-client}{client-to-}\typeout{\ifin@ YES\else NO\fi} The problem is generally characterized on pp. 9f. of http://mirror.ctan.org/macros/latex/contrib/nicetext/fifinddo.pdf Perhaps this is known (concerning \in@) and has been taken into account when it was used. I also don't know how to produce a LaTeX mistake from this (using user or package writer commands only). A hint on this may be that the problem already occurs with patterns that end on the same character as they begin with, e.g., \in@{msam}{msa} (this idea because \in@ seems to be mainly used in handling fonts, while there seems to be no danger with searching comma-separated lists). LaTeX bug or not? Happy TeXing, Uwe.