I looked a bit closer at your code and noticed that you add STDIN to your select call instead of readHandle. Any reason? It might be that this is your problem.

I tried the following test script and it works. I get output every 5 seconds:

#!/usr/bin/perl

use warnings;
use Data::Dumper;
use IO::Handle;
use IPC::Open2;
use IO::Select;

my $i;
my ($readHandle, $writeHandle) = (IO::Handle->new, IO::Handle->new);
my $pid = open2($readHandle, $writeHandle, 'bc');

$writeHandle->autoflush(1);
$readHandle->autoflush(1);

my $select = IO::Select->new();
$select->add($readHandle);
while (1) {
    print $i++,"\n";
    my ($handle) = $select->can_read(5);
}
[download]

Interestingly it works even when I turn off blocking, which means my previous notion that can_read would not wait if blocking is turned off might be false.

The $readHandle is defined in the parent, not the child. The child is reading from STDIN, so I don't believe this will work, and in my testing, it did not.

I do, however, have a workaround. I set the timeout to 0 based on your advice and put a very small delay at the end of the "infinite" loop:

    while(time < $endTime)
    {

[...]

        select(undef, undef, undef, 0.05);

    }
[download]

Since I could not get blocking to work no matter what I tried (which may still be some fault of my own), this seems to be a workable fix for now. It reduced CPU to almost nothing, which is an enormous gain since the load was consistently over 80 on the box where this was running multiple instances.

I will continue to modify my test code to see if I can implement your suggestions more effectively. Your help has been invaluable in at least finding a workaround and possibly a permanent solution, jethro, and I really appreciate your time