Am 07.06.2012 03:20, schrieb Donald Arseneau:
>>>> The approach that we have taken for this is to use "@@" as the indicator
>>>> for internal code:
> Too bad "@@" is currently the indicator for a renamed TeX primitive.

yes they are, but we thought this nevertheless acceptable in an L3 
context. While expl3 runs on top of 2e there is a slight chance that you 
may want to refer to 2e commands in expl3 code and within the 2e 
commands to the handful of @@ frozen primitives. However, those either 
exist as expl3 names, eg \tex_par:D instead of \@@par, or we could 
provide them (or you have to not use the @@ convention in that part 
where you really need them).

at least that was our conclusion so far.