It's not a monad, it's an ordinary macro. Also, you got the syntax wrong. What you wrote expands to (bar baz quux foo). To GP: I've heard it called "double arr

It's not a monad, it's an ordinary macro. Also, you got the syntax wrong. What you wrote expands to (bar baz quux foo). To GP: I've heard it called "double arrow" or "post-threading operator".