What is an example of a difference in allowed usage or behavior between an xvalue and a prvalue FOR NON-POD objects?

Question

What are rvalues, lvalues, xvalues, glvalues, and prvalues? gives a good overview of the taxonomy of rvalues/lvalues, and one of the recent answers to that question (https:/

Answer 1

What is the true difference between an xvalue and a prvalue? The xvalue is a kind of rvalue that can be cv-qualified and refer to an object and have dynamic type equal or unequal the static type.

const int&& foo();
int&& _v=foo();

Without xvalue, the return value of the above function foo can only be a rvalue. But build-in types have not const rvalue! Thus, the above non-const variable _v can always bind the return value of foo(), even we wish the foo() return a const rvalue.