But in Emacs-25, the above "(car ,@$3)" was read assuming the ,@ is
a new-style unquote, i.e. it's read as "(car (\,@ $3))", whereas the
earlier "( ,@$2 )" was read as "(\,@$2)", i.e. as a single list
containing a funny symbol named ",@$2".
I think this was a bug, which would be fixed by dropping support for
old-style backquotes, so that "( ,@$2 )" would now be read as "((\,@
But I'm not sufficiently familiar with the bovine code to be sure
(especially since misinterpreting "( ,@$2 )" as "(\,@$2)" would likely
have been noticed, so either it's really what was intended, or else
there's presumably somewhere some hack that tries to work around this
quirk). In bovine-grammar-expand-form, I see:
which makes me think that maybe "(\,@$2)" is indeed what was intended,
and this code is designed to turn "(car (\,@ $3))" into "(car \,@$3)",
so that both ways to read work (the new-style reading is transformed
into the old-style reading).