Certainly you should go to Apple’s developer support sites and see if there are problem-reports concerning any impacts upon Perl (version??) as a consequence of XCode-4.

It also seems to me that this problem, whatever it is, might be filled with a lot of red herrings.   When words like “sloppy” crop up in conversation about fundamental production Perl code-libraries, my immediate instinct says, “do we truly understand this problem?”   We might believe that we do, and might indeed be right, but warning-bells are going off right now that in similar situations I personally have jumped to utterly wrong conclusions.   Everyone should be “from Missouri” now.   Skeptically assume that the hypothesis isn’t correct, unless it can be demonstrated beyond doubt.