Lets see...

def toggle_oven(value)
  if value == true
    return "The oven is now on"
  else
    return "The oven is now off"
  end
end

# I don't really like this one, though, I think it should work
def toggle_oven(value)
  return "The oven is now on" if value == true
  "The oven is now off"
end