I think you could structure this a little more clearly. The title and introduction seem to present this as "pros and cons of modifying the system Perl", and then the lists are pros and cons of installing your own Perl. If someone (like, say, me...) isn't reading carefully, they may start on the "pro" list and think "'Modifying the system Perl can break the OS.'? How the hell is that a point in favor of modifying the system Perl?" before noticing that it's a list of reasons to build your own, not a list of reasons to modify the system Perl.

Also, I'm not clear on how "You are (safely) limited to the module versions provided in packages by your vendor" fits into the "pros of building your own" list. If you build your own Perl, you aren't limited (safely or otherwise) to module versions provided by the vendor.