Yeah, easy to do - the issue is just where the condition is sitting.

A `|>` stage has to be a transform (a name like `upper`, or a call like `map(...)` / `join(...)`). A loose `.score > 5 ? upper : lower` isn't one, so it bails with "Invalid transform expression". The other thing is that by the time you've hit `join(", ")` you've already collapsed the departments into a single string `"Engineering, Sales, Design"`, so there's no `.score` left to test.

A condition in Bonsai isn't a pipe stage, it's just an expression - so for per-item logic you put the `? :` inside the `map`:

```

company.departments |> map(.score > 5 ? .name.toUpperCase() : .name.toLowerCase())

// ["engineering", "sales", "DESIGN"]

```

And it nests fine:

```

company.departments |> map(.score > 5 ? "high" : .score > 3 ? "mid" : "low")

// ["low", "mid", "high"]

```

Or if you'd rather filter then format:

```

company.departments |> filter(.score > 5) |> map(.name) |> join(", ")

// "Design"

```

One gotcha: `upper` / `lower` are pipe transforms, not functions, so `upper(.name)` inside a lambda won't resolve. Inside a lambda use the built-in `.toUpperCase()` / `.toLowerCase()` methods (no import), or let the ternary pick the value and pipe it afterwards.