<pedant>
Just a thought but instead of the "-------------" in your example you could use "__END__" instead. At least then the example will compile without editing.
</pedant>
Also, dont forget to mention to your prof that -w and use warnings; have different and somewhat incompatible semantics. It is a highly contentious subject I know, but I think if you are looking forward (ie in terms of version etc) then forget -w and use warnings; only. It is also much more powerful than -w.(look into warnings::register and related functions.)

I suggest you point your prof at perlvar and at the sort function documentation ($a and $b are not for some reason documented in perlvar).

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demerphq
my friends call me, usually because I'm late....