By the way, I did notice, while trying to run your program, that I was getting an error with the URL you have:

my $url = 'http:www.oreilly.com/catalog/prindex.html';
[download]

It doesn't work for me in a browser, either (it's a missing or unavailable page).

The reason I mention it is that the error message from Perl was somewhat cryptic ... so if you get an error retrieving that page, you may want to try another page which you're positive is accessible.