#  bad, you are only joining 1
# $thr->join;
# $thr1->join;

#better
foreach my $thread ( threads->list ) {                                                    
   $thread->join;                                                                         
}        


# or you could stuuff the threads into hashes
# like 

my %thrs;
for(1..30){ 
   $thrs{$_}{'thread'} = threads->new(\&thread_sub);
 }

#then join them by looping thru the hash keys