HCL

The native syntax is inspired by libucl and nginx, designed for easy reading and writing, as shown in the clean, block-based config.hcl example.

Supports a JSON-based variant that shares the same data model, allowing seamless mixing of human-authored native syntax and machine-generated JSON configs.

Includes inline expressions for computation, variables, and functions, enabling declarative logic in configurations without full scripting, as demonstrated with arithmetic and string interpolation.

Applications can define expected attribute names and block types, leading to better error messages and validation, which is a core part of HCL's philosophy for robust configs.