In December 2024, Jo Heinz contributed to the idris-lang/Idris2 repository by developing a new high-level parser combinator called 'between' using Idris and functional programming techniques. This combinator cleanly parses content enclosed by two parsers, and Jo refactored the existing 'parens' parser to leverage this new abstraction. The work improved the parser module’s modularity and reusability, reducing code duplication and simplifying future maintenance. By focusing on parser combinators and functional programming principles, Jo positioned the parser library for more rapid feature development. The depth of the changes reflects a thoughtful approach to maintainability and extensibility within the Idris2 codebase.