$ perl -le'
    my @a;
    print 0+@a;
    print defined($a[0]) || 0;
    $a[70] = "a";
    print 0+@a;
    print defined($a[0]) || 0;
'
0    0 elements in the array
0        and the first one isn't defined.
71   71 elements in the array
0        and the first one still isn't defined.

##</code><code>##

$ perl -le'
    my @a;
    print defined($a[0]) || 0;
    $a[0][0];
    print defined($a[0]) || 0;
'
0
1