i just realized upon reviewing your description that you want to run a round of burns, then reload all drives at the same time, then do another round, etc. to achieve this, replace the main loop with this:

my $chld;
while (@data) {
        while (@resource) {
                last unless @data;
                my $resource = shift @resource;
                my $data = shift @data;
                if (($chld = fork()) > 0) {
                        # parent code
                        $jobs{$chld} = $resource;
                } else {
                        # child code
                        runcmd($resource, $data);
                        exit;           # end chld, trigger $SIG{CHLD}
                }
        }
        sleep until @resource == $num_resources;
        print "ONE ROUND DONE";
        last unless @data;
        print "RELOAD THEN PRESS ENTER: ";
        <>;
}
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