template<sender Sndr, queryable... Env>
requires (sizeof...(Env) <= 1)
constexpr sender decltype(auto) transform_sender(Sndr&& sndr, const Env&... env)
noexcept(see below);
template<sender Sndr, queryable Env>
constexpr queryable decltype(auto) transform_env(Sndr&& sndr, Env&& env) noexcept;
template<class Tag, sender Sndr, class... Args>
constexpr decltype(auto) apply_sender(Tag, Sndr&& sndr, Args&&... args)
noexcept(see below);