Package include implements a HCL extension that allows inclusion of one HCL body into another using blocks of type "include", with the following structure: include { path = "./foo.hcl" } The processing of the given path is delegated to the calling application, allowing it to decide how to interpret the path and which syntaxes to support for referenced files.

Package transform is a helper package for writing extensions that work by applying transforms to bodies.

Package typeexpr extends HCL with a convention for describing HCL types within configuration files.

Package userfunc implements a HCL extension that allows user-defined functions in HCL configuration.