C++11: shortest way to explicitly copy a value to use as an rvalue reference

I have a function

class A { <has copy and move constructors > };

void f(A &&a) { ... }

I want to call the function f with a variable x, but I want to run f on a copy of x, not x itself. Why can't I do something like this?

f(copy(x));

But instead must do

f(A(x));

Is there anything similar to the copy function I describe above?

Note: please don't tell me to add an overload f that does the copying, I want something that doesn't require an overload and is explicit (i.e. copy makes it clear to the reader that copying is done here)