You might want to look at the module LWP and there are some further examples of use here, but you probably want to get the site directory first parse through it, getting a list of the .txt files and then get each one in turn, while searching them. If you can ftp to the site it might be easier to parse though anyhow by using Net::FTP and get a listing of the files and FTP them over for further use.

-enlil