Here is some test code !

#!/usr/bin/perl

use 5.014;
use strict;
use warnings;
use autodie;

use AnyEvent;
use AnyEvent::HTTP;
use FileHandle;
use File::stat;

my $multiChunkSize=4194304; # Maximum size of a single block (in bytes
+)
my $multiLimit=6; # Maximum number of parallel HTTP requests
my ($wholeChunks,$chunkRemainder,$runID,$condvar,@offsets,@blocklist);
my $activeCount=0;
my $debug=1;
my $localfile="test";

# Byte size

sub byteSize {
        use bytes;
        my ($inval)=@_;
        return length($inval);
}

# Quotient remainder calculator

sub qrem {
    use integer;
    my( $dividend, $divisor ) = @_;
    my $quotient = $dividend / $divisor;
    my $remainder = $dividend % $divisor;
    my @result = ( $quotient, $remainder );
    return @result;
}

# Get file size
sub fileSz {
        my($file) = @_;
        my $stat = stat($file);
        return $stat->size;
}

# Get data
sub readData {
        my ($file,$length,$offset)=@_;
        my $fh = FileHandle->new;
        my ($data);
        if ($debug) { say "Reading ${file} offset ${offset} for length
+ ${length}";}
        #open ($fh,"<",$file);
        $fh->open("< $file");
        binmode($fh);
        read($fh,$data,$length,$offset);
        if ($debug) { say "readData read ".byteSize($data);}
        #close($fh);
        $fh->close;
        return $data;
}

# Process

sub doProcess {
        return if $activeCount >= $multiLimit;

        my $offset = shift @offsets;
        return if !defined $offset;

        $activeCount++;

        if ($debug) { say "Active:${activeCount}, Offset:${offset}";}
        $condvar->begin;
    my $contentLength=$multiChunkSize-1;
    my $content = readData($localfile,$contentLength,$offset);

}

# Populate offsets
sub populateOffsets {
        my ($count,$offsetSize)=@_;
        if (!defined $count || !defined $offsetSize) {exit 1;}
        my $offset=0;
        my @offsets;
        for my $i (1..$count) {
                push @offsets,$offset;
                $offset = $offset + $offsetSize;
        }
        return @offsets;
}

######### MAIN

        # Calculate chunk quantity
        my @chunks = qrem(fileSz($localfile),$multiChunkSize);
        $wholeChunks=$chunks[0];
        $chunkRemainder=$chunks[1];
        @offsets=populateOffsets(${wholeChunks},${multiChunkSize});
        $condvar = AnyEvent->condvar;
        # DO IT 
        for (1..$multiLimit) {
                doProcess();
        }
        $condvar->recv;
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