HCL is the most ramshackle, poorly thought out "languages" I've encountered. The only thing it has going for it is it attempts to implement a declarative/functional model instead of the lunacy of pulumi encouraging people to have a go with (various) imperative languages.

If you need convincing of the ill-considered nature of HCL, go look at the discussion around adding deep map merge support to terraform and the suggestions to use a third-party provider for this.