If someone were to jump the queue you were standing in, would you speak up or let it go?

Let’s for debates sake assume it’s a fairly lengthy queue, maybe at the bank or the supermarket. A blatant case of someone edging ahead of you. Now I realise life’s too short for petty squabbles, but hey, it’s also too short for waiting around in queues longer than needs be! So yeah, maybe a bit of a no brainer I dunno. How would you react…... or indeed how have you reacted in such an instance?