How to switch views in scene view window

Now recently, I was messing around with unity, when I accidentally clicked a key. Now this would have been fine, if it hadn’t have switched my viewing mode… to orthographic.

I hope this isn’t a stupid question, but I am very stuck and cannot continue my project, whilst I use this awkward viewing mode. I HAVE gone through the keys on the keyboard, but to my dismay, could not find a way to change this.

Just click in the middle of the axis controller in the top right hand corner of the scene view!