Regarding R and its soundness (in the general colloquial sense), here's something that bothers me about it (scope leakage):

    > if ("blah" == "blah") {
          y = 2
          x = y + 2
      } else {
          x = 1
      }

    > x
    4
    > y
    2

I really wish what I introduce in my blocks would stay in my blocks...

If that's the worst issue, I'm not seeing much of a problem. I guess I'm not particularly hyped about intro of "let" (block scope) into Javascript, vs "var" (function scope), either, but it bothered somebody enough to need "let".

Does R have an "IIFE" type construct, similar to JS or Golang?