trying to distinguish between different kinds of rvalues - literals and non-literals

I want to have a method that can be called only with lvalues so I've done the following:

template <typename T>
MyClass& cache(T&) {}

template <typename T>
MyClass& cache(const T&&) = delete;

And this works fine - I can even pass C string literals since they are also lvalues.

The reason I need lvalues is because I'm caching pointers to the passed objects - and that means they cannot be temporaries.

The following code works:

MyClass a;
a.cache("string literal");

int temp = 6;
a.cache(temp);

And the following code (as desired) does not work:

int getInt(); // fwd decl
a.cache(getInt());

But I also want to be able to pass other literals - but they all seem to be rvalues...

The following code does not work (but I wish it could):

MyClass a;
a.cache(6);

Is there a way to distinguish between such literals and non-literal rvalues?

Is there a way to easily turn such literals into lvalues? I found this answer on Stack Overflow mentioning something like unless you write 1L but even if I give an L suffix to a literal it is still a temporary.

Even a macro is OK - something like this: a.cache(TURN_TO_LVALUE(6));