If your Perl apps are unusually slow on CentOS 5, have a look at this blog:
http://blog.vipul.net/2008/08/24/redhat-perl-what-a-tragedy/
In a nutshell: some Perl apps are 100x slower on RedHat / CentOS 5 compared to other distributions.
Bugzilla entry:
https://bugzilla.redhat.com/show_bug.cgi?id=379791