[CamTin]

Or Scheme :)

One of the motivating cases is working around the Nix language's shortcomings:

> The Nix package manager: Nix is a declarative package manager using its own language for specifying packages. Nickel is inspired in part by the Nix language, while trying to overcome some of its limitations. It could be used instead of the Nix language.

Guix sidesteps this all by just using a proper language with macros for its configuration.

[snicker7]

Or GNU Shepherd. With Lisp-based configuration, you get all the power of imperative programming with all the transparency of declarative programming.