Ok, so the answer is, "because Rubyists have redefined that phrase"? ;-)

The sweetening of the syntax in Sinatra seems to be rather straightforward. I assume it's something like:

  # internal route stuff

  @routes = {}

  def get(method, &block)
    @routes[method] = block
  end

  # user provided code

  get 'foo' do
    puts 'foo'
  end

  # something hooked up to execute at the end of the file

  while input = gets.chomp
    @routes[input].call if @routes.include? input
  end

I find it really hard to call that a language – it's just a clever use of normal Ruby syntax.