Help: Pipeline breaking after upgrade to 4.2. The 'eval' function syntax changed?

Just upgraded our Cribl Stream leader to 4.2 and a bunch of our data quality pipelines are broken. Errors point to `eval` functions, specifically around the new syntax for `C`. Looks like the shorthand for `__C` changed?

Before 4.2, we used things like:
* `C.input` to reference the input metadata
* `C._raw` for the raw event

Now it's throwing "Undefined variable 'C'" errors. The docs mention a change but are vague on the exact migration.

Has anyone else hit this? What's the exact new syntax?

What we're seeing:
* Pipelines with `eval` functions using `C.` are failing.
* Search functions seem okay.
* Using `__C` directly seems to work, but need to confirm.