use strict;
use warnings;

my @v = (1, 2, 3);
my $r = \@v;

check();

@v = ();

check();


sub check
{
        print ((! $r) ? "Empty " : "Non-empty ", "reference\n");
        print ((! @$r) ? "Empty " : "Non-empty ", "array\n");
}
[download]

Non-empty reference
Non-empty array
Non-empty reference
Empty array

Personally I'd test the assignment by !defined $raData and the emptyness by scalar(@$raData) == 0.

However, as far as I can see, !@$raData seems to test for emptyness as I'd expect with Perl 5.6.1, so I maybe I missed the point of your question?

Best, -gjb-

Your test is sound, but the answer is probably that it depends what happens when 'assignment fails'. An array in boolean context (is there such a thing in perl?) will evaluate to true if it contains anything at all:

() is false
(undef) is true
(0) is true
[download]

so if it's coming from a sub that explicitly returns 0 or undef on failure, you'll end up with a populated array. The best thing to do is use just return, since return undef is true in list context. I dimly recall that there occasions when return () is dodgy in scalar context, too, but I can't remember what they are :(

hth