Set value in random ViewController (random segue)

I have 12 ViewControllers. My code gives a random segue to one of these ViewControllers (1-12)

let segues = ["View1", "View2", "View3", "View4", "View5", "View6", "View7", "View8", "View9", "View10", "View11", "View12"]
    let index = Int(arc4random_uniform(UInt32(segues.count)))
    let segueName = segues[index]
    self.performSegueWithIdentifier(segueName, sender: self)

.

Now, I want to change a variable in the random ViewController that has been chosen (var firstSegue = false) but I can't figure out how?

.

Could someone change this into something that will work?

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    let destinationVC = segue.destinationViewController as UIViewController
    destinationVC.firstSegue = true
}