There is nothing wrong with string eval when you have complete control over what's going into it,

Oh, I agree with you. I also happen to agree with our coding standards, because far too many people with Perl on their resume are incompetent fools whose experience with Perl stops at making a config change to one of Matt's Scripts. Had I not already put carefully-crafted char classes into prod, I'm sure I could make a case for an exception (they do grant them after a business approval and a code review, which is quite reasonable).