After a fresh installation of Gentoo I have decided to use Collectd to monitor my system status, so I have emerged it as stated in Gentoo wiki page, than I have also emerged Collectd-web which is a great frontend for Collectd. Here my problems started 
Collectd-web was working (interface was present) but it displayed no graphs, after checking apache error_log I have found this:
[Tue Nov 15 22:35:24 2011] [error] [client *.*.*.*] [Tue Nov 15 22:35:24 2011] collection.modified.cgi: Can't locate HTML/Entities.pm in @INC (@INC contains: /etc/perl /usr/lib64/perl5/site_perl/5.12.4/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.12.4 /usr/lib64/perl5/vendor_perl/5.12.4/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.12.4 /usr/lib64/perl5/site_perl /usr/lib64/perl5/vendor_perl /usr/lib64/perl5/5.12.4/x86_64-linux-thread-multi /usr/lib64/perl5/5.12.4 /usr/local/lib/site_perl .) at /var/www/localhost/htdocs/collectd-web/cgi-bin/collection.modified.cgi line 25., referer: [my_host_name]
First spot was to emerge PERL again – no effect…
Than I have started searching over the Internet. First good tool was perl-cleaner, I had run:
perl-cleaner --all
which emerged all missing libraries and deleted those not used. After that I have found that I am still missing some modules i.e. URI::Escape, searching around lead me to this site:
http://forums.slimdevices.com/archive/index.php/t-16975.html
so I run
cpan URI::Escape
and that was all I needed to start Collectd-web displaying data properly
