User-defined literals + embedded scripts

[LB]

I was wondering, since user-defined literals can be evaluated at compile-time, would it be possible to embed scripts that are interpreted at compile time and executed at runtime? What sort of restrictions would be imposed on the parsing algorithm and the runtime evaluation algorithm? Would interpreting the script at compile time instead of at runtime be worth it? Would it significantly affect the time it takes to compile? From a design perspective, would it be bad in the first place to have embedded scripts instead of external scripts?