Hmm, even if the package for doing this comes with Ruby MRI, I'm not sure there's a corresponding out-of-the-box way to take these s-expressions and get running code. But here's a five-year-old article talking about Ruby2Ruby, a library that converts these s-expressions to strings: http://www.igvita.com/2008/12/11/ruby-ast-for-fun-and-profit...
I don't think a third-party tool should count as language support, unless (and inasmuch as) the people maintaining the language regularly go out of their way to avoid breaking that tool. This is where I draw the line, because of how it affects backwards compatibility.
 Well, I guess the term "third-party" might not apply in that case!
 I have no idea how much I'm actually talking about Ruby2Ruby, and this Ruby s-expression format in general, when I make this comment.