you are correct about the parens on prn:x... I thought I had a clever trick from making them unecessary, but it didn't pan out when I sat down to work out the necessary transformations... creating decent language primitives is hard...
...your "line noise" comment also is a good point...
This stuff is hard. I looked into implementing general splicing functionality but it is not trivial. Reading @bar and translating it to (splice 'bar) is easy enough, but then you would have to examine the arguments of every sexp before evaluating it to handle the splice. I guess it's not particularly difficult but it would likely be a performance hit. Perhaps there is a clever trick to do general splicing.