T.101 Proposal for how to pass arguments to a variadic template

I have a suggestion to fill in the missing known information for T.101. The standard library passes parameter packs by perfect forwarding in almost all cases, and that should be the norm. For read-only operation, it generally makes more sense to use const& though, because read-only operators virtually never have an rvalue overload, and accepting const& is more const-correct anyways.

T.101 Pass parameter packs via const reference or forwarding reference

Reason

Allow passing lvalues and rvalues, and avoid unnecessary copy/move construction.

Example

// all arguments passed as const&, because we don't mutate any arguments
template<typename L, typename... Rs>
auto equal_to_any(const L& l, const Rs&... rs) const 
{
    return (l == rs || ...);
}

// we can mix lvalues like zero_object and rvalues like 0
bool is_x_zero = equal_to_any(x, nullptr, 0, "", "zero", zero_object);

// args are passed as forwarding reference, because the consumer might
// need to modify them, move them, ...
template <typename Consumer, typename... Args>
void consume_all(Consumer consume, Args&&... args)
{
    (consume(forward<Args>(args)), ...);
}

Enforcement

Flag parameter packs which are passed by value or lvalue-reference.

Start by reviewing the existing T.101 guideline and its surrounding parameter-pack guidance in the C++ Core Guidelines. Compare the proposed const-reference and forwarding-reference examples with current wording, then update T.101 so the recommendation and enforcement statement are unambiguous.