For instance:

#include <ranges>

constexpr std::string_view first_n_words(std::string_view str, size_t n) {    
    namespace rv = std::views;
    auto first_n = str
                | rv::split(' ')
                | rv::take(n)
                | rv::join;   

    return std::string_view(&*first_n.begin(), std::ranges::distance(first_n));
}

constexpr std::string_view first4 = first_n_words("Hello to all you beautiful libstdc++ developers", 4);

This doesn't compile because _M_emplace_deref isn't marked constexpr (probably becase P2231 isn't implemented yet, but thought I'd file a bug report anyway).