use Parallel::ForkManager;
my $pm = new Parallel::ForkManager(4);
foreach my $base_dir (@base_dirs) {

    my $storable_file = $storable_dir.$f;
    $pm->start and next; # do the fork

    `/home/qiang/file2.pl $storable_file $base_dir`;

    $pm->finish;
}
$pm->wait_all_children;

##</code><code>##

use File::Find;
use Storable qw(store retrieve);

my $storable_file = shift;
my $base_dir = shift;
my @usr_dirs = map {chomp;$base_dir."/".$_} `/bin/ls $base_dir`;
my $mbox = {};

find(\&wanted,@usr_dirs);
store $mbox, $storable_file or die "Can't store !\n";