In that blog post you link to, it talks about HTTP libraries implementing caching... which, it appears, LWP doesn't do. However, it got me thinking, and a quick search shows that someone has written something and put it on CPAN to hook into LWP::UserAgent for just this purpose (HTTP::Cache::Transparent).

To comply with this reasonable suggestion, perhaps LWP should incorporate HTTP::Cache::Transparent directly into its own distribution, and include instructions on initialising the cache (perhaps with some sane defaults available, I'm not sure, e.g., cache_in_home_dir => '.perl/my-app' which would do something sane on windows (stripping the leading dot, and prepending whatever makes sense on Windows) and unix, not sure about other platforms) as part of the LWP synopsises. Well, that's just my two cents anyway.