[perl #131592] [ASYNC][REGRESSION] Piping from one Proc to another occasionally dies with "his process is not opened for write"

[jn...@jnthn.net via RT]

On Sat, 17 Jun 2017 22:18:31 -0700, c...@zoffix.com wrote:
>     zoffix@VirtualBox~/CPANPRC/rakudo (nom)$ cat bar.p6
>     for ^4000 {
>         my $p = run(:out, :bin, 'ls'); run(:in($p.out), 'true')
>     }
>     zoffix@VirtualBox~/CPANPRC/rakudo (nom)$ ./perl6 bar.p6 
>     Unhandled exception in code scheduled on thread 12
>     Tried to get the result of a broken Promise
> 
>     Original exception:
>         This process is not opened for write
> 
>     zoffix@VirtualBox~/CPANPRC/rakudo (nom)$ 

Fixed by recent changes to handle code like this by plumbing descriptors 
together. A further fix has made it not end up running out of descriptors also.