When a third-party app ships their own version of Perl (or Java), the third-party is responsible for maintaining it, not the sysadmin. The reason sysadmins just use the Perl provided in the distro is because they know (from experience) that maintaining more than one version is a headache. Maintaining more than one version of anything (at the same time) is a headache. So you can either use the distro provided Perl (and let the OS vendor maintain it), or you can throw caution to the wind and replace it with with your own (and then you the sysadmin must maintain it). There are pros and cons to each and the decision to go one way or another will have a lot to do with the sysadmin's experience. But intentionally running multiple versions of Perl in a production environment is fostering bad habits (IMO).