Perl threads

#!/usr/bin/perl -w

use strict;
use threads;

sub say_hello
{
    my $index = 0;
    my $tmp   = 0;

    foreach $index (1 .. 100)
    {
        printf("Hello thread! @_.\n");

        $tmp = rand(10);

        sleep($tmp);
    }

    return $tmp;
}

my $th_01 = threads->create("say_hello", "param1");
my $th_02 = threads->create("say_hello", "param2");
my $th_03 = threads->create("say_hello", "param3");
my $th_04 = threads->create("say_hello", "param4");

my $th_result_01 = $th_01->join;
my $th_result_02 = $th_02->join;
my $th_result_03 = $th_03->join;
my $th_result_04 = $th_04->join;