use strict;
use warnings;

use threads;
use Thread::Queue;

use constant MAXTHREADS => 1; # Update this to the maximum number of threads you want. Keep it below the number of physical cores available on your machine.

my @inputFiles = qw(); # Do something to populate your list of inputs

my $inputQueue = Thread::Queue->new( @inputFiles );
my $printQueue = Thread::Queue->new();

$inputQueue->end(); # Tell everyone that the inputQueue wont have anything else added to it

my $printThread   = threads->new( \&printWorker );
my @workerThreads = map { threads->new( \&worker ) } 1..MAXTHREADS;

$_->join for @workerThreads;

$printQueue->end(); # Tell everyone that the printQueue wont have anything else added to it

$printThread->join();

###### END OF MAIN ######

sub worker
{
    # Add code to prepare for individual file processing
    # This function should be the equivalent of your (working) serial process

    while ( defined( my $file = $inputQueue->dequeue() ) )
    {
        # Add code here to process individual files
        $printQueue->enqueue( 'output' ); # Instead of printing, enqueue output data to the print queue
    }
}

sub printWorker
{
    my $outFile = "myOutFile"; # Set name of output file
    open my $fhOut, ">", $outFile or &{ warn "Failed to open file for writing: $!"; exit 1; }; # Kill all threads on failure
    select $fhOut;

    print $_ while $_ = $printQueue->dequeue();

    close $fhOut;
}