> Python, C++, Ruby and Java all use exceptions. To them, “exception” means, “nifty piece of syntax kinda like goto.”

Not Ruby. In idiomatic Ruby^ exceptions are for exceptional cases, not code flow. "nifty piece of syntax kinda like goto." is the much underused but very powerful catch+throw.

Or rather, it's a stack unwinding mechanism: think baseball, the catcher expects a ball, with the ball being a message to be passed. Upon that you could implement a specialized and more costly case of stack unwinding which does what fail/raise+rescue does, but catch+throw is more general than exceptions.

Take Python's StopIteration as an example: there's absolutely no need for this to be a full exception, instead it's like `break`ing a loop but across method calls.

^ Nevermind Rails practices. Rails is not Ruby.