In case you didn't know, the point of 'atpos is to implement atstrings, an optional string interpolation feature that lets "@qty @(plural qty \"taco\") @@ $@price" compile so that it evaluates to things like "2 tacos @ $11". This option isn't enabled by default, so any Arc program that uses atstrings, such as news.arc, has to (declare 'atstrings t) first.
IMO, an @ at the end of an atstring is a syntax error, since it isn't escaping anything. It might be convenient to give "...@" a meaning like (sym "..."), (err "..."), or even just "...@@", but that's adding functionality rather than fixing bugs.
