I just noticed another point where the expl3 naming rules doesn't say what to do: what if I have a variable that is also a function? In traditional imperative languages those may seem like exclusive categories, but in (La)TeX programming it is sometimes perfectly natural, and quite straightforward. The typical example of this would be a callback function: something that a module calls at specified points, but which the user of that module is expected to define. Treating this as just a function loses the specification of the scope for that variable. Treating it as a variable of type tl loses the specification that it takes arguments. What I found natural is to use a name of the form \<SCOPE>_<MODULE>_<DESCRIPTION>:<ARG-SPEC> e.g. \l_harmless_callback:nn This could be interpreted both as adding a SCOPE part to function names (the vast majority of functions without a SCOPE are implicity considered to be c_ constant), or alternatively as proclaiming any :<ARG-SPEC> to be a valid _<TYPE> for a variable. Lars Hellström