Use select to multiplex over many reading file handles (see code below butchered from the cook book). Checkout the following nodes for more info:

• select for info about the older non OO version of select
• IO::Select for info about the OO version listed below
• perlman:IPC::Semaphore and IPC::SysV if you want to implement some kind of process locking (you hint that you do but should not have to with select)
• Here For a comprehensive treatment of the use of select. (Old non OO stylee)
• Look at Section 7.13 of the cook book for the original reference to the code mapped out below

use IO::Select;

open FHANDA,"processA|" || die("..");
open FHANDB,"processA|" || die("..");
open FHANDC,"processA|" || die("..");

$Select = IO::Select->new();
$Select->add(*FHANDA);
$Select->add(*FHANDB);
$Select->add(*FHANDC);
if (@ready = $slect->can_read(0))
{
  for (@ready)
  {
    #Process the file handle (do the read and write)
  }
}
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Update Just a thought but in the reaper sub (not written above) it would be nice to $Select->remove() the file handles as the processes die.
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Zigster