To use HTML::Tidy, we must first make sure the libtidy is installed in the system. Otherwise, when you try to install it via cpan, it will give you compilation error.

On Gentoo, in order to install it from cpan, you must make sure you have "emerge -v app-text/htmltidy".  Or better, just directly "emerge -v dev-perl/perltidy" and that should take care of everything for you, I think.

On CentOS, in order to install HTML::Tidy, we have to install libtidy by hand. The website in libtidy suggested to download the source code via cvs, which is open to anonymous users. Yet when I tried it, the cvs required password. I was not able to find libtidy in yum search, even after I installed CentOS Extra Repos. Anyway, I found the rpm in http://centos.karan.org/el4/extras/stable/i386/RPMS/repodata/repoview/li.... (For CentOS 4, nor 5.) Download both the regular as well asa the devel packages, and then do "yum install libtidy*".

Now that we have the libtidy (and its header files), we can use cpan to install HTML::Tidy.