Using defined on an aggregate's been out of fashion for a good while now.

$ perl -e 'use strict;use warnings;my @foo;if( defined @foo ) { print 
+"foo" }' |& splain
defined(@array) is deprecated at -e line 1 (#1)
    (D deprecated) defined() is not usually useful on arrays because i
+t
    checks for an undefined scalar value.  If you want to see if the
    array is empty, just use if (@array) { # not empty } for example.
    
        (Maybe you should just omit the defined()?)
[download]

And even before it went out of fashion, it never was the correct test whether it contained elements anyway. An array could be defined, yet empty - although it being undefined implied it being empty.