The latest version of the library is libwww-perl-5.48.tar.gz (146 KB) which was released Apr 9, 2000. You will need perl version 5.004 or better to use this version. You can also look at the individual files of the latest distribution directly and the ChangeLog which should tell you if an upgrade is worthwhile.
The latest libwww-perl package as well as perl itself are also available on CPAN (Comprehensive Perl Archive Network). This is also the place to obtain the other packes that libwww-perl depend upon (URI, HTML::Parser, MIME::Base64, Digest::MD5, and Net::FTP from libnet) as well as other modules that I wrote.
Paul J. Schinder maintains the MacPerl port of libw