The list of functions build into this category really can change your perspective on how you engineer your presentational layer code. The ability to test for the availability of a feature, variable, function or mixin is paramount when you start down the path of engineering complex reusable frameworks. It it with these functions we can finally have real tests in our code that can help a user get their work done more efficiently.
But introspection functions don't stop there. Functions that evaluate for the type of a value, or a value's unit for example, really start to show the impressive ability in this category.
Again, we ask for your patience as we begin to explore more and more advanced use cases for these amazing tools.