A lightweight Babel plugin that wraps top‑level block statements (e.g., `{ … }`) in an immediately‑invoked function expression (IIFE). This prevents variables declared with `let`/`const` from leaking onto the global `window` object after they’re down‑leveled to `var` in ES5 builds. It’s useful for developers who transpile modern JavaScript to ES5 and need to preserve block‑scope privacy without altering their source code.