>> Thinking about it some more, I am wondering: is it more important >> - to distinguish keys which only differ by their catcode, or >> - to allow for any token as a key (e.g. Hef{}feron, which currently >> breaks the delimited argument approach) ? > > Hello Bruno, > > I'd say that at the very least we should _store_ tokens and not > _strings_. So category codes should be preserved when putting stuff in > or getting them out. After all, sequences might be used for all sorts of > things, and the tokenization may be important. Of course, the <value> must be a token list, but the <key> could be more restricted? I'm guessing that the use of a prop may be \q_prop name \q_prop {S\o m\c{e}$t_{hi}n^g$} \q_prop country \q_prop {Br\'azil} \q_prop I.D. number \q_prop {2CUOHE@#@} \q_prop ef{}ficiency \q_prop {12} (etc.) Here <values> may be anything, but <keys> are rather well behaved. The key (sic) property of <keys> in my understanding is whether they differ or not, and detokenizing will not cause too many collisions? Regards, Bruno