IPC::Msg as a fork safe queue. Couple caveats that make it less cool, the by-default maximum queue size seems to be very small. Configurable though by changing /proc/sys/kernel/msgmnb which is the max size in bytes of an individual queue up to 2^31 - 1 on my system at least. Check with  ipcs -l. You also have to delete the queue when finished. Or not if you want to use it later. You can also find the same queue in different scripts with ftok, not shown. You can also see queue sizes / number of messages with ipcs command, add flags to pull off different messages from the queue. You don't always have to do FIFO, you can add different kinds of messages to the same queue, and you can block or not block if you want to have multiple queues being worked at the same time.

For complex data structures you would need to serialize or pack / unpack which other cpan modules may already address and better. Message queues are already documented in perlipc, but a little sugar show show versatile it can be. Basically add or remove from the queue with any child process not worrying about blocking / synchronization issues, but you can accidentally destroy the queue before it is empty, or leave an empty or not-empty queue hanging around that you would have to delete with icprm command.

#!/usr/bin/env perl
use strict;
use warnings;
use feature 'say';
use IPC::SysV qw/IPC_PRIVATE S_IRUSR S_IWUSR IPC_NOWAIT/;
use IPC::Msg;
$|++;

use constant MSG_BYTES => 1024;

my $q = IPC::Msg->new(IPC_PRIVATE,S_IRUSR|S_IWUSR);

sub quit { $q->remove; }
$SIG{INT} = \&quit;

sub enqueue {
    my $msg = shift;
    my $msg_type = shift // 1; # Used for message selection, see msgsn
+d(2)
    $q->snd($msg_type,$msg,IPC_NOWAIT) || die $!;
}

sub dequeue {
    my $type = shift // 1; # See msgop(2)
    my $msg;
    $q->rcv($msg,MSG_BYTES,$type,IPC_NOWAIT);
    #if ($!) { warn "$$ - $!" }
    return $msg // undef;
}

sub dequeue_block {
    my $msg;
    my $type = shift // 1; # See msgop(2)
    $q->rcv($msg,MSG_BYTES,$type);
    #if ($!) { warn "$$ - $!" }
    return $msg // undef;
}

sub isEmpty {
    my $stat = $q->stat;
    return $stat->qnum == 0;
}

sub isPrime {
    my $num = shift;
    return 1 if ($num < 4);
    return 0 if ($num %2 == 0);
    for (my $i=3; $i <= sqrt($num); $i+=2) {
        return 0 if $num % $i == 0;
    }
    return 1;
}

my $n_workers = shift // die ;

enqueue($_) for (1..2_000_000);

my $parent = $$;

for (my $i=1; $i<$n_workers && $$ == $parent; $i++) {
    fork // die;
}

while (my $data = dequeue()) {
    if (isPrime($data)) {
        print "Prime: $data\n";
    }
}

END {
    if ($$ == $parent) {
       1 until wait == -1;
       quit;
    }
}
[download]

• Num Procs: Time(seconds)
• 2^0 : 55.171
• 2^1 : 35.073
• 2^2 : 21.455
• 2^3 : 15.121
• 2^4 : 12.380
• 2^5 : 11.080

Update 2019-02-04 - You can't wait on grandchildren, changed code to only fork from parent. Fixed spelling of empty.