To be honest, I find it hard to think of anyone who gets any of the questions other than #1 wrong as as fairly decent. At best, they know how to use Perl for a quick one off task (which is a pretty useful skill, no doubt), but I wouldn't rely on them for writing anything that has to be reliable.

#1 is not a waste of time at all, though I'd rather make it a bonus question. This specific parsing rule has certainly tripped up every Perl beginner at least twice, and probably plays a trick even on more advanced programmers once in a while. I know it took me quite a while to understand the semantics exactly. I'd consider someone who answers that question fairly capable at understanding Perl code (which includes their own) although it doesn't necessarily mean they are used to good coding practices (like strict).

Regarding strict, I would extend the question to also ask when it is not useful. Truly insightful coders know when to break the rules.

Similarly, in #5, I'd also ask for an explanation of $var = @array;, and for a comparison between the two.

Overall, I think the questions are decently chosen. I would consider someone who answers them all well unlikely to make a big mess with Perl.

Makeshifts last the longest.