Part of libwww-perl (LWP) is now available in a separate distro, HTTP-Message. Installing this new distro can break LWP. If you want to protect yourself from something with a dependency on a module in HTTP-Message, upgrade LWP.

If you don't, you may end up with the following error:

500 Can't locate object method "_is_html" via package "HTTP::Headers"
[download]

We got it using

$ perl -MLWP -le'print LWP->VERSION'
5.813

$ perl -MLWP::Protocol -le'print LWP::Protocol->VERSION'
5.810

$ perl -MHTTP::Headers -le'print HTTP::Headers->VERSION'
6.00
[download]

You can always upgrade LWP after getting this error, but that will effectively uninstall HTTP-Message. You may then reinstall HTTP-Message.

The only way the author could avoid this problem is by adding a dependency on LWP to HTTP-Message, but that would be inappropriate.

This has been a public service announcement :) Posted so people encountering this issue don't have to spend time diagnosing it.