> * Conclusions
>
> As you can see, I did not really mean any concurrent execution. Simply being
> able to execute parts of code in-situ, in the Org buffer, to document (and
> test) what I'm writing.
>
> And to be able to assemble all the parts in one single script file, by the
> means of literate programming.
>

I see, you want to be able to construct a large pipe chain STDOUT>STDIN,
but you don't care if the parts of the chain (e.g., the code block)
execute in serial or concurrently (as they do in the shell).

The attached patch (can be applied with "git am") implements this
behavior as I understand it.  The result is a new :stdin header argument
with which org-mode references can be passed to shell scripts as
standard input.  Given the technique used in this patch, I'll probably
re-write part of ob-awk.el.

The following Org-mode snippet demonstrates it's use, please let me know
if this works for your use-case described above.