The best multiline strings are those where you can have proper indentations without having to guess how indentation is handled. bonus points for making nesting easy and making copy-pasting work without breaking indentation.

To my knowledge only Zig's multiline strings work this way

    const hello_world_in_c =
        \\#include <stdio.h>
        \\
        \\int main(int argc, char **argv) {
        \\    printf("hello world\n");
        \\    return 0;
        \\}
    ;