gistfile1.txt

use strict;
use warnings;
use utf8;
use LWP::Simple;
use URI::Escape;
use Encode;

my %SUFFIX = (
    37 => '.mp4',
    35 => '.flv',
    34 => '.flv',
    22 => '.mp4',
    18 => '.mp4',
    17 => '.3gp',
    13 => '.3gp',
     6 => '.flv',
     5 => '.flv',
);

my $video_id = shift;

my $info = "http://www.youtube.com/get_video_info?video_id=$video_id";
my $down = "http://www.youtube.com/get_video?video_id=$video_id&t=%s=&fmt=%d";

my $param = +{};
for my $p (split '&', decode_utf8 uri_unescape get $info) {
    my ($key, $value) = $p =~ m/^(\w+)=(.*)/;
    if ($key eq 'itag' && $param->{$key}) {
        $param->{$key} = $value if $value > $param->{$key};
        next;
    }
    $param->{$key} = $value;
}

my $fmt = $param->{itag} || 18;

mirror(sprintf($down, $param->{token}, $fmt), $video_id . $SUFFIX{$fmt});