An oversight I noticed when working with this SRFI: The specification says that define-optionals and define-optionals* are supposed to be provided in the (srfi 227 definition) library, which is missing. The forms are defined in the source, but not used. There's an old open pull request that adds exports for them from (srfi 227) instead of adding the sublibrary.
The R6RS version does provide them in its equivalent library.
