Do you get the error with a newer Perl?

That message indicates a bug in Perl or in an XS module.

but it failed throwing the below error:

Hm . Runs fine under 5.8.9.

Also, in my original prg, I was trying to download 200 different files changing the URL each time, but in the prg that you gave, looks like it downloads a single file 200 times.. is that right ?

Sorry. I don't have a handy source of 200 different files at my disposal.

#! perl -slw
use strict;
use threads ( stack_size => 4096 );
use threads::shared;
use LWP::Simple;
use Time::HiRes qw[ time sleep ];

our $T ||= 200; ## This can be change by a command line arguement -T=n
+nn

my $url = ## your url here ##;

## This shared variable counts 
## the number of running threads
my $running :shared = 0;

## This records the start time
my $start = time;

## For 1 to 200
for( 1 .. $T ) { 
    ## start a new thread
    async(
        ## running this sub
        sub{
            ## Increment the running threads count
            { lock $running; ++$running };
            
            ## Make all threads wait until all threads are running
            ## so that the download requests all hit the server at the
+ same time
            sleep 0.001 while $running < $T;
            
            ## The number (1..200) passed in as $_ below.
            my $id = shift;
            
            ## get $url and store it in a file with $id as part of the
+ name
            getstore( $url, qq[c:/test/dl.t.$id] );
            
            ## Now this thread is finished, decrement the count
            lock $running; --$running;
        }, $_   ## $_ (1..$T) becomes $id inside.

    ## Detach means that the threads go away as soon as they are done.
    ## Rather than hanging around consuming resources waiting to retur
+n
    ## a return value to join that we have no interest in.
    )->detach; 
}

## Now the main thread just sleeps till all the d/l threads have finis
+hed.
sleep 1 while $running;

## And tells you how long the whole thing took
printf "Took %.3f seconds\n", time() - $start;
[download]

Thanks alot man for your help and patience. Finally I used apache bench marking tool. Started 1000 connections and successfully tested the network. Thanks all!