Definition of post-processor, i.e. function, that is applied to already rendered license header, performs some logic and returns modified text of license header. Given that the reader monad and ReaderT transformer is used, any configuration is provided using the env environment. When combined with the Headroom.Data.Has monad, it provides powerful way how to combine different post-processors and environments.

Structure of post-processor

Text -> Reader env Text
  │              │   │
  └─ rendered text of license header
                 │   │
                 └─ environment holding possible configuration
                     │
                     └─ modified license header text