#! perl -slw
use strict;
use threads;
use threads::shared;

our $N ||= 100;

our $from=1;
our $to=200000;

sub worker {
    my $tid = threads->tid;
    my( $log, $semRef, $from, $to ) = @_;
    for my $file ( $from .. $to ) {
        ## Simulate doing some processing
        ## Lock the log file semaphore before writing
        lock $$semRef;
        ## And write to the log
        printf $log "[%2d] Processesing file%3d\n",
            $tid, $file;
        ## The lock is released automatically at the end of the block
    }
}

## A shared variable used as a semaphore for the log file resource
my $logSem :shared;
## Open the log file in the main thread
open my $log, '>', 'myLog2' or die $!;
my @threads = map{
    ## create the workers passing the log file handle and semaphore
    threads->create( \&worker, $log, \$logSem,$_*$N, $_*$N + $N -1);
} 0 .. 5; ## 5 threads each processing 100 "files"
## Wait till they are done
$_->join for @threads;

## close the log
close $log;
[download]