You missed plugging it into the whole script. I said "do this first", didn't I?

Well, apparently that wasn't clear, so here is the whole current script, as I see it.

#! /usr/bin/perl

@a = qw/a b c/;
@a = test();
printf "defined: %s\nsize: %d\n" , defined @a ? 'yes' : 'no' , scalar 
+@a ;


sub test {
    return () ;
}
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