The line:

my $file = <FILE>;
[download]

only reads one line from the file. You will need to loop through the file looking for your words. Secondly your pattern for a word is..interesting. I could just give you an RE that kind of works, but I suspect that you are really in need of a good basic introduction to the topic.

Theoretically complete documentation on how REs work can be found at perlre. But that is hard for most people to follow. japhy is in the process of writing a book on how to learn basic REs. You can see the start of it here, and his tool YAPE::Regex::Explain is invaluable.

And, of course, let me recommend merlyn's book, Learning Perl. It has an excellent review of basic Perl that should help you a lot.