IIRC the usual workaround in Elixir involves be small lambda that rearranges things:

    "World"
    |> then(&concat("Hello ", &1))

I imagine a shorter syntax could someday be possible, where some special placeholder expression could be used, ex:

    "World"
    |> concat("Hello ", &1)

However that creates a new problem: If the implicit-first-argument form is still permitted (foo() instead of foo(&1)) then it becomes confusing which function-arity is being called. A human could easily fail to notice the absence or presence of the special placeholder on some lines, and invoke the wrong thing.