Actually, it has been updated. As I understand it, based on the paper by Aas, LWPng is the attempt to provide support for HTTP/1.1 clients in libwww-perl. Now, the paper by Gisle Aas may be a decade old, but the work has continued on libwww-perl which is currently at libwww-perl-5.805 as of 12-8-05. Now, LWPng has morphed into ParallelUserAgent, the LWPx series of modules, and the Bundle::LWP. Here's the link to Aas' paper:

LWPng-Adding HTTP/1.1 Support to libwww-perl