If the array were lexically declared it would not persist between calls to the subroutine.

Really?

use Devel::Peek qw( Dump );

sub f {
   my $x;
   Dump($x);
   $x = "abc";
}

f();
f();
[download]

SV = NULL(0x0) at 0x2cb90dc
  REFCNT = 1
  FLAGS = (PADMY)
SV = PV(0x1542f64) at 0x2cb90dc
  REFCNT = 1
  FLAGS = (PADMY)
  PV = 0x154b194 "abc"\0
  CUR = 3
  LEN = 12
[download]

You can tell it's the same variable in both calls to the function not only by the address being the same, but by the state left over between calls. Would you care to change you claim that this $x isn't a lexical?

See Re: A curious case of of my()