Some people think that configuration should not be "Turing complete"; others think the configuration language should be as expressive as possible--so much so that it amounts to a programming language itself.
I assert that configuration files which are not Turing complete (or, perhaps a more useful distinction, are not "sufficiently complex languages") are in practice extended to be that complex; and when that happens, the result is often more difficult to understand than if the language were more powerful to start with.