`@pnpm/which` is a lightweight Node.js utility that mimics the Unix `which` command, searching the `PATH` environment variable for the first occurrence of a given executable and returning its resolved path (or throwing). It’s intended for developers who need reliable program‑location lookup in scripts — such as build tools, CLI utilities, or automation workflows — without the quirks of the native Windows implementation. The library also offers an `all` option to retrieve every matching path and supports custom `path`/`pathExt` overrides for advanced use cases.