This is a command application that will download a file and save to the specified filename showing a Tk progress bar window on the Desktop. (Tested @ 4.5GB)

tk-download-w-progressbar.pl

#!/usr/bin/perl

use strict;
use warnings;
use threads;
use threads::shared;

use Tk;
use Tk::ProgressBar;

use LWP;
use Fcntl qw(SEEK_END);

use constant AFTER_TID => 5000;

# now, check for passed URLs for downloading.
die "Regrettably, no URL was passed for processing.\n" unless $ARGV[0];
die "Regrettably, no output filename was passed for saving.\n" unless $ARGV[1];
die "Regrettably, the output file exists.\n" if -e $ARGV[1];

my $p:shared = 0;
my $url:shared = $ARGV[0];
my $path:shared = $ARGV[1];
my $total_download_size:shared = get_file_size($url);
my $download_size:shared = 0;
my $fin:shared = 0;

my $thr = threads->new(\&worker)->detach;

my $mw = MainWindow->new(-width => 300, -height => 96);
my $f1 = $mw->Frame(-borderwidth => 2, -width => 296, -height => 92, -relief => 'groove')->pack(-side => 'top');

my $message = <<"EOT";
This is an example, written in the context of MAGNet #perl IRC, to download and save a large file to disk.
EOT

$f1->Label(-text => $message,-wraplength => 280)->pack(-side => 'top');
my $pb = $f1->ProgressBar(
    -height => 10,
    -length => 280,
    -width => 10,
    -from => 0,
    -to => 100,
    -blocks => 28,
    -colors => [0, 'blue'],
)->pack(-side => 'top');

my $out_file;

my $repeat1;
$repeat1 = $mw->repeat(
    100 => sub {
        $repeat1->cancel if $p == 100;
        $pb->value($p);
    }
);

my $repeat2;
$repeat2 = $mw->repeat(
    100 => sub {
        if ($fin) {
            $repeat2->cancel;
            my $r = $mw->messageBox(-type => 'Ok', -message => 'The file download has been completed successfully.');
            if ($r eq 'Ok') {
                exit;
            }
        }
    }
);

MainLoop;

sub worker {
    open($out_file, "> $path") or die "Couldn't open $path for writing: $!\n";
    binmode($out_file);
    select($out_file);
    $|++;
    select(STDOUT);
    my $ua = LWP::UserAgent->new();
    my $response = $ua->get($url, ':content_cb' => \&callback, );
    close ($out_file);
    $fin = 1;
}

# per chunk.
sub callback {
    my ($data, $response, $protocol) = @_;
    seek($out_file, 0, SEEK_END);a
    $download_size += length($data);
    $p = sprintf("%d",$download_size / $total_download_size * 100);
    print $out_file $data;
}

sub get_file_size {
    my $url = shift;
    my $ua = new LWP::UserAgent;
    $ua->agent("Mozilla/5.0");
    my $req = new HTTP::Request 'HEAD' => $url;
    $req->header('Accept' => 'text/html');
    my $res = $ua->request($req);
    if ($res->is_success) {
        my $headers = $res->headers;
        return $headers->content_length;
    }
    return 0;
}