This is harder to parse in my mind than:

  if is_ok:
    do_the_thing()
  else:
    warn_the_user()

In that you can see more or less visually what the intent is rather than having to mentally parse the text. But perhaps that's just personal taste.

IMHO, expressiveness and conciseness are largely the same idea because when you talk about the former, you mean being able to bang out an idea in fewer lines of code yielding the latter.

Having a complex grammar and a myriad of ways to do the same thing seems very neat, but in the end the productivity gained in the writing, you waste several times in the reading, so it ends up being a net loss.

But Perl lost the dynamic language wars a long time ago -- I think perhaps some of the flavor got picked up in Ruby?

And having a language read like English is IMO, a bad idea -- English is very ambiguous in many cases -- mimicking this in your programming language would be a bad idea indeed.