Dear oshalla, thank you for your codes, it really helped me to grasp several ideas about threading in Perl. My only addition would be that's in your 1st and 2nd examples you clone the arguments (@array) in the first two cycles, meaning you're creating two threads with the same arguments: for (1..2) - in the 1st example and while ($c) - where $c=2 - in the 2nd example To fix that I used a new variable to count dispatched threads.

#!/usr/bin/perl

use strict ; use warnings ;

use threads ;
use Thread::Queue ;

my @array = qw(a b c d e f g h);
my @results;

my $finished_queue = new Thread::Queue ;

my $c = 5 ;     # Number active at once
my $n = 10 ;    # Total number to dispatch
my $m = $n ;    # Number to collect
my $d = 0;    #count created threads
while ($n) {
while ($m) {
$d++;
    my $child = threads->create(\&sub_thread, @array) ;

my $tid;my $childa;
if ($d == $c)
{
  $tid = $finished_queue->dequeue() ;
  $childa = threads->object($tid) ;
  push @results, $childa->join() ;
$d--;
$n--;
}
  $m-- ;
} 
if (!$m)
{
my  $tid = $finished_queue->dequeue() ;
my  $childa = threads->object($tid) ;
  push @results, $childa->join() ;
$n--;    
}
}

sub sub_thread {
  my (@temp) = (@_) ;
  my $tid = threads->tid() ;

  print "child $tid: @temp\n" ;

  sleep(rand(2)+2) ;

  $finished_queue->enqueue($tid) ;

  print "child $tid: finished\n" ;
  return "whatever from child $tid" ;
} ;

exit;
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It's not elegant, but it works and all I needed was a quick fix. P.S. It's an old thread, but it was the most useful for me just now, so I'd rather share the solution in this old thread.