How can I add a progress bar to WWW::Mechanize?

I have the following code:

$mech->get($someurl, ":content_file" => "$i.flv");

So I'm getting the contents of a url and saving it as an flv fil开发者_Go百科e. I'd like to print out every second or so how much of the download is remaining. Is there any way to accomplish this in WWW::Mechanize?

WWW::Mechanize says that the get method is a "well-behaved" overload of LWP::UserAgent get. Looking at the docs for LWP::UserAgent, you can provide a content_cb key which is called with each chunk of the downloaded file:

$mech->get( $someurl, ":content_cb" => \&callback );
sub callback
{ 
  my( $data, $response, $proto ) = @_;
  # save $data to $i.flv
  # print download notification
 }

Many thanks to Peter Kovacs' answer for leading me to the correct answer. It turned out to be a bit more elaborate than I'd expected though so I decided to (horror) answer my own question.

As Peter showed, I can set a callback like so:

$m->get($u, ":content_cb" => \&callback);

But now I can't save the content using the :content_file value, because I can only choose one of the two. The callback function gets passed the data, and I ended up writing that to a file instead.

I also get a response object which contains the total size of the content as friedo pointed out. So by keeping a running total of content received so far and dividing it by the total content I can find out what percent of the content has been downloaded. Here's the full callback function:

open (VID,">$i.flv") or die "$!";
$total = 0;
sub callback
{
    my( $data, $response, $proto ) = @_;
    print VID "$data"; # write data to file
    $total+= length($data);
    $size = $response->header('Content-Length');
    print floor(($total/$size)*100),"% downloaded\n"; # print percent downloaded
}

I hope that helps someone.