Excellent advice. It also isolates you from problems when you have different groups maintaining the OS and the applications, so you don't have the OS admins pushing out a newer perl RPM through up2date and managing to clobber all your site installed modules simultaneously . . . (fortunately I didn't have to clean up too much on that one :).

At $cur_job I try and keep a separate "application" copy of all the really critical underlying software packages (Perl, gcc, PVM, ruby) that's independent of the RPM-installed system copies (granted we have a frelling huge NFS share for this which makes it easier than custom local RPMs; we're dependent on the same NFS mount for sharing gigs of data across n-hundred boxen anyhow so we live with the failure point for the binaries as well).