Shaykat posts on $exception. It's a little debugger trick to let you see the inners of the current exception when one fires.
Funny thing about the name. Often folks use 'ex' to name an instance of an exception type. So, we figured we'd call it '$ex'. Then we realized that '$' kinda looks like 's', and having a feature called 'sex' might not go over as well.
To this day, I still think of it as 'sexception'. Silly me.