Here is how to return data from forks in PFM. If you want to put it in a variable that the main script has in scope, use threads and threads:shared.

The following code has been posted here before.

#!/usr/bin/perl
use 5.010;
use strict;
use warnings;
use Parallel::ForkManager;
#use Data::Printer;

my $pm = Parallel::ForkManager->new(2);

$pm->run_on_finish(
    sub {
        # result from the child will be passed as 6th arg to callback
        my $res = $_[5];
        # p $res;
        print "$res\n";
    }
);

for (1..3) {
    $pm->start and next;
    # from here and till $pm->finish child process running
    # do something useful and store result in $res
    my $res = { aaa => $_ };
    # this will terminate child and pass $res to parent process
    $pm->finish(0, $res);
}

$pm->wait_all_children;
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