Arc is now released. For those not in the known, Arc is a dialect of Lisp, written by Paul Graham and Robert Morris. In Paul Graham's own word,
"Arc is designed above all for exploratory programming: the kind where you decide what to write by writing it. A good medium for exploratory programming is one that makes programs brief and malleable, so that's what we've aimed for. This is a medium for sketching software." or in short, "it's a quick and dirty language for writing quick and dirty programs."
Taken from tutorial,
arc> (+ 1 2)
arc> (+ (+ 1 2) (+ 3 (+ 4 5)))