People tend to learn the portions of Perl that are most applicable to their section of the problem set. I'm sure there are very experianced Perl programmers who never used the formating feature, but there are also people who learned Perl a month ago who use it every day.

Your test seems to start with some easy questions and then gets a little more indepth later on. I would suggest throwing a few harder questions in there (perhaps a multiple-map statement similar to the Schwartzian Transform). Don't count it against them if they get it wrong, but use it as a flag to find people who really know what they're doing.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated