Just for the record. The only reason I even mentioned it. Was because the perl docs did

Nothing in there says he'd have to use -U to delete files. Quite the opposite, it says it re-enables a feature that damages your filesystem. There's a reason the feature (unlinking directories) isn't normally allowed.

Which IMHO, is not the same as recommending the use of it. :)

The docs don't, but you sure did. You said the OP had to use -U, and that's harmful, incorrect advice.