$ perl -Mv5.14 -e'my @a; \$a[0]; say exists( $a[0] ) || 0;'
1

##</code><code>##

use Devel::Peek;

my @z;
$a = \$z[1];
say "\$z[$_] exists: ", exists( $z[$_] ) || 0 for 0..2;

say '---Dump @z';
Dump @z;

say '---Dump $z[0]';
Dump $z[0];

say '---Dump $z[1]';
Dump $z[1];

##</code><code>##

$z[0] exists: 0
$z[1] exists: 1
$z[2] exists: 0
---Dump @z
SV = PVAV(0x2770318) at 0x27a4930
  REFCNT = 1
  FLAGS = ()
  ARRAY = 0x2787080
  FILL = 1
  MAX = 3
  FLAGS = (REAL)
  Elt No. 0
  SV = 0                           ### 0 
  Elt No. 1
  SV = NULL(0x0) at 0x2783d70      
    REFCNT = 2
    FLAGS = ()
---Dump $z[0]
SV = NULL(0x0) at 0x7a91d0         ### NULL (WTF?)
  REFCNT = 2147483641
  FLAGS = (READONLY,PROTECT)
---Dump $z[1]
SV = NULL(0x0) at 0x2783d70
  REFCNT = 2
  FLAGS = ()