I recommend treating it as a spectrum instead of boolean. Eval is considered harmful for a similar reason as to why GOTO is: it makes code harder to prove and t

I recommend treating it as a spectrum instead of boolean. Eval is considered harmful for a similar reason as to why GOTO is: it makes code harder to prove and to manipulate. Markup and data on one end of the spectrum can be endlessly manipulated, analyzed, and worked with. As we move up the power spectrum, we get to regular languages, stack languages, and finally Turing-completeness. Within Turing-completeness, though, there are still varying levels of how hard something is to work with. Yes, the halting problem means that you can't for any behavior determine whether an arbitrary program exhibits that behavior, but there are still subsets about which you can reason.