This is a beautifully elegant solution, but it fails for "I can't see you". It can't shuffle that sentence. The only valid answer should be "I cna't see you" but this solution treats apostrophes as word-breaking. Luckily the kata doesn't test for apostrophes, but the "All punctuation should remain in place" rule is unclear about how apostrophes should be handled. This puzzle is much harder if testing for this extra layer.

It's described in the docs at http://ruby-doc.org/core-2.2.3/String.html#method-i-gsub.

If the second argument is a Hash, and the matched text is one of its keys, the corresponding value is the replacement string.

I didn't know you could use gsub with a Hash as second argument like that. Learned something new :)