Holiday is over, now I have fun again. No code changes. (0.38.11)

docs/performance.md

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+# Performance Guide
+
+Tips for getting good performance from Fun programs and builds.
+
+## Build configuration
+- Use `-DCMAKE_BUILD_TYPE=Release` for production binaries.
+- Consider `FUN_DEBUG=OFF` to remove extra checks in hot paths.
+- `FUN_USE_MUSL=ON` can help with static/portable builds; measure performance for your use case.
+
+## Language-level tips
+- Prefer pre-sized arrays/maps when possible to reduce reallocations.
+- Avoid unnecessary string concatenations in loops; accumulate in arrays and `join`.
+- Push work to native ops where available (e.g., regex, JSON, math helpers).
+
+## Algorithmic choices
+- Choose appropriate data structures (arrays for ordered scans, maps for key lookups).
+- Cache repeated computations or lookups when safe.
+
+## Measuring
+- Create small, representative benchmarks.
+- Compare Debug vs. Release to ensure changes are meaningful.