As you said the syntax is wrong, let me tell you now, from a pure syntax point of view, this is perfectly correct Perl syntax.

Didn't you realize that NULL could be a constant?

use strict;
use constant NULL => "";

my @a = (1,2,3);
my @b = ();
my @c = ("");
print "a is empty: " . is_null(@a), "\n";
print "b is empty: " . is_null(@b), "\n";
print "c is empty: " . is_null(@c);


sub is_null {
    my @a = @_;
    (@a == NULL) ? "true" : "false";
}
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