|laziness, impatience, and hubris|
That's fine if you're golfing.
I tend to be a bit more explicit in code that I'm leaving around for someone else to read. That last statement has about six semantic steps that partially nest, partially flow right to left, and partially flow left to right, without the help of denotational punctuation to help me "change gears".
It's also riddled with booby traps for the maintainer. The parens on output are mandatory, or else the redo would trigger before the function is called. If the expression for the test gets more complicated, or wants to be called only once, there's a bit of gyrating to do.
I figure anything that takes me more than a dozen seconds to parse needs to be broken up for production code. My personal rule.
See, if you were just going for compact, I'd slide that even further to:
This gets rid of the naked block entirely.
But again, I would not use this in production code. This is cute to impress your friends, especially your Lisp-hacking friends. But it really aggravates the maintainer who has to try to grok that at 3am when the production web site crashes.