- Configuration languages (JSON, YAML, XML) are pure combinatorial logic.
- Regular expressions are... mostly not actually regular, but you get the idea.
- Some templating languages are deliberately less powerful than Turing machines, e.g. ST4 is context-free.
- Prepared SQL statements are a similar idea on a different axis.
The real question is whether a non-TC language could be useful for general purpose programming. Such a language might come with very strong guarantees (termination, time complexity, even correctness or a limited form of correctness), but they might be extra-cumbersome for 'normal' workloads.
- Configuration languages (JSON, YAML, XML) are pure combinatorial logic.
- Regular expressions are... mostly not actually regular, but you get the idea.
- Some templating languages are deliberately less powerful than Turing machines, e.g. ST4 is context-free.
- Prepared SQL statements are a similar idea on a different axis.
The real question is whether a non-TC language could be useful for general purpose programming. Such a language might come with very strong guarantees (termination, time complexity, even correctness or a limited form of correctness), but they might be extra-cumbersome for 'normal' workloads.