#!/bin/env perl
#
# call:
# script.pl name.tld
#
use warnings;
use strict;
use IPC::ShareLite;
use Storable qw(thaw freeze);
use File::Temp qw(tempfile);
use Fcntl ':flock';
use POSIX ":sys_wait_h";

# allow the child-processes to store their results
# so that the parent can access them
my $store = new IPC::ShareLite( -key => "__dnssearch__",
                -create  => 'yes',
              -destroy => 'no' ) or die "Store: " . $!;


my $results = {};
$store->store(freeze($results));

# fake addresses, tested with two real servers
my @dnss = qw(111.111.111.111
       222.222.222.222
       111.222.111.222
       222.111.222.111);

my $host = $ARGV[0];
my @children = ();
# used to "flock" access to the shared storage in the children
my $lock = tempfile();

foreach (@dnss) {
 my $dns = $_;
 my $parent = fork();
 if (!$parent) {
         my $command = "nslookup -type=A $host $dns 2>/dev/null";
         my $res = qx/$command/;
         my $store = new IPC::ShareLite( -key => "__dnssearch__",
                            -create  => 'yes',
                            -destroy => 'no' ) or warn ("Child $_: ". 
+$!);
         flock($lock, LOCK_EX);
         my $results = thaw($store->fetch());
         $results->{$dns} = $res;
         $store->store(freeze($results));
         flock($lock, LOCK_UN);
          exit(0);
 } else {
         die "couldn't fork!" unless $parent;
         push(@children, $parent);
 }
}

# leave no zombies, collect all children
# nslookup times out, so there will be an end
for (@children) {waitpid($_, 0);}

# access results
$results = thaw($store->fetch());
#
# do something with results
# 
use Data::Dumper;
print Data::Dumper->Dump([$results,],["result"]);
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