Rather than compare it to arc, I found it tantalizing to think about how I'd implement that syntax. It looks like he's built objects for modules/namespaces, ranges, etc. But he's somehow supporting infix without spaces and also names like print-line. How does it work?! :)
Edit 8 minutes later: Also, the square brackets around the call to [f 1] are strange. If they're mandatory, there's something there I don't follow.