Background
A while ago I wrote a Raku module to test out some ideas I had for making external process pipelines (e.g., grep raku | wc -l). I followed the traditional way of creating Pipes and setting up I/O redirections for the external processes.
Since there's no fork available in Raku, nor is it recommended due to threads in MoarVM, I resorted to using Proc::Async to start a wrapper process for each external command in a pipeline, and the wrapper would then sets up I/O redirections to connect the command processes and the pipes, and then close other FDs before exec-ing the real command.
Problem
This all seems to work well except there's still the possibility that other parts of the program using the module might start a sub process (e.g., via run, shell, Proc, or Proc::Async) in another thread after the pipe FDs are created but before they are closed, thus leaking them and causing the command processes in the pipeline to block on read / write.
Question
How would you prevent FDs from leaking to any child processes started in another thread in Raku?
Thanks