#! /usr/bin/perl 
use strict;
use warnings;

use threads;
my @child;
my @list = qw(a b c d);

while (1) {
  foreach(@list){
    push(@child,threads->create("test","$_"));
  }

  foreach my $ch (@child) {
    $ch->join();
  }
  @child = ();

}

sub test
{ 
  my ($item) = @_;
}