Worked on the mozilla/rhino repository to deliver Unicode-aware, case-insensitive regular expression support, enhancing the engine’s ability to accurately process international text. The approach involved enabling combined Unicode and case-insensitive flags, implementing approximate Unicode case-folding, and updating core Java matchers to operate correctly in Unicode-insensitive mode. This included introducing a new opcode and extending matcher logic to handle complex cases such as special characters like ß. Test coverage was expanded to validate the new behavior and prevent regressions. The work demonstrated depth in Java programming, Unicode handling, and regex development, resulting in more robust and globally usable regex functionality.