[ejones]

There's a proposal for this: https://github.com/tc39/proposal-partial-application

[abecedarius]

That's more specialized: it can express

    foo(42, ?)

but not what you'd write within this pipe syntax as

    foo(42, ^) + 1

The tradeoff is that it doesn't need some extra delimiter since the function call is what delimits it. Perhaps that's a better tradeoff, I'm not sure; but for sure we shouldn't have both.