Update: Modified script. Completes in 1 second with Cygwin Perl v5.22.4 and less than 1 second on Unix.

Update: Modified list of modules to pre-load. On the Windows platform, run with Perl v5.26 or later for best results.

The following is a demonstration using MCE::Loop. The behaviour is similar to running a pool of workers. Workers request the manager process the next URL to process. The job_delay option gives each worker time to load any missing modules at runtime before another worker starts processing. The delay occurs one time by each worker.

use strict;
use warnings;

use LWP::Simple;

# Pre-load essential modules for extra stability.

if ( $INC{'LWP/UserAgent.pm'} && !$INC{'Net/HTTP.pm'} ) {
   require IO::Handle;
   require Net::HTTP;
   require Net::HTTPS;
}

my @urls = (
   'http://hooboy.no-such-host.int/',
   'http://us.a1.yimg.com/us.yimg.com/i/ww/m5v9.gif',
   'http://www.guardian.co.uk/',
   'http://www.ora.com/ask_tim/graphics/asktim_header_main.gif',
   'http://www.pixunlimited.co.uk/siteheaders/Guardian.gif',
   'http://www.yahoo.com',
) x 4;

use MCE::Loop;

MCE::Loop->init(
   max_workers => 8,
   chunk_size  => 1,
   posix_exit  => 1,
);

mce_loop {
   my ($type, $length, $mod) = head( my $url = $_ );
   print "$url is done\n";
} \@urls;

MCE::Loop->finish;
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Regards, Mario