class Array
  def jumble
    self.sort {|x, y| (rand 3) - 1}
  end
  def middle
    self.slice(1, size - 2) || []
  end
  def last_el
    size > 1 ? last : ''
  end
end
class String
  def cambridge_jumble
    a = split('')
    a.first + a.middle.jumble.join('') + a.last_el
  end
end
'I consider myself up on psycho linguistics but I hadnt heard of that one'.split.map {|x| x.cambridge_jumble}.join ' '