Errata

In the progress bar examples, you call ua->head() to get the content-length, then
make a separate call to ua->get() to get the data, passing the content-length to the
progress callback via the lexical variable $total_size. This is not necessary. The
$response value passed to the callback contains the Content-Length header, so you can
avoid the call to ua->head() altogether by rewriting callback() as

sub callback {
my ($data, $response, $protocol) = @_;
$final_data .= $data;
print progress_bar(
length($final_data),
$response->header('Content-Length'),
25,
'=');
}