Thanks all for the replies.

I've tried to synthesize the different approaches.

To flesh this out a bit, I'm planning on using callbacks (run_on_wait) to manage notifying/killing a hung process. Using the alarm(TIMEOUT) doesn't really solve my problem. If I set the timeout to 60, no other processes will run until that 60 seconds has elapsed as the wait_all_children still isn't satisfied.

wait_for_available_procs (which was newer than my version of Parallel::ForkManager--so I upgraded) didn't seem to make any difference.

The callbacks indicate that everything stalls until the looping test4.sh script is killed.

use strict;
use warnings;
use Parallel::ForkManager;
use constant TIMEOUT => 60;

my @runArray = ("test1.sh", "test2.sh", "test3.sh", "test4.sh", "test5
+.sh");
my ($pid, $exitCode, $ident);

my $forkMgr = Parallel::ForkManager->new(3);

$forkMgr->run_on_start(
    sub {
        ($pid, $ident) = @_;
        print "Started ==> $ident\n";
    }
);

$forkMgr->run_on_finish(
    sub {
        ($pid, $exitCode, $ident) = @_;
        print "Ended ==> $ident\n";
    }
);

while (1) {
    for my $runCommand (@runArray) {
        $forkMgr->start($runCommand) and next;
        alarm(TIMEOUT);
        system("/usr/localcw/opt/patrol/nagios/libexec/$runCommand") o
+r die ("exec: $!\n");
    }

    $forkMgr->wait_all_children;

    sleep 10;
}

exit;
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