LWP and the other modules mentioned here are available from CPAN, the Comprehensive Perl Archive Network, at http://www.cpan.org/.
For more information about HTTP and LWP, consider reading Clinton Wong's book, Web Client Programming with Perl, published by O'Reilly. Some of the information is dated, but it is still a good introduction to HTTP and techniques for using LWP in applications.
All listings referred to in this article are available by anonymous download in the file ftp://ftp.ssc.com/pub/lj/listings/issue67/3673.tgz.