if someone gets them wrong, however, you can't tell whether they know Perl well or not

I'd say the first two are important to know.

The next two fall into the "I wouldn't do that, therefore that code is suspect. I'm not sure what it does, but documentation needs to be added to explain what it's doing and/or it needs to be refactored."

The last one is just plain unimportant. The code dies quite loudly and reproduceably. A better discussion would be how to fix it.