use Devel::Peek;
my $value = "four";
my @array = ( "one" );
warn "(1):\n" ; Dump($value);

foreach $value (@array)
{
    warn "(2):\n" ; Dump($value);
    print "foreach value: $value\t";
    function();
    sub function {
        warn "(3):\n" ; Dump($value);
        print "function value: $value\n";
    }
}

__END__
(1):
SV = PV(0x8b83b00) at 0x8b83768
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x8b992c8 "four"\0
  CUR = 4
  LEN = 8
(2):
SV = PV(0x8b83c20) at 0x8b82c28
  REFCNT = 2
  FLAGS = (POK,pPOK)
  PV = 0x8b962c0 "one"\0
  CUR = 3
  LEN = 4
(3):
SV = NULL(0x0) at 0x8b837b0
  REFCNT = 2
  FLAGS = (PADBUSY,PADMY)
foreach value: one      function value:
[download]

As you can see, all addresses of $value are different. The my() just tells the compiler that the symbol $value is to be treated as a lexical variable for the scope in which it was declared, but that doesn't mean it has always the same storage (or only one address location). <update> The $value inside the sub inside the for() loop gets its own $value because the outer $value isn't visible in the scope in which it has been compiled.</update> Bare blocks are different:

use Devel::Peek;
my $value = "four";
warn "(1):\n" ; Dump($value);
{
    $value = "five";
    warn "(2):\n" ; Dump($value);
}
__END__
(1):
SV = PV(0x8bcdb00) at 0x8bcd75c
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x8bee7d0 "four"\0
  CUR = 4
  LEN = 8
(2):
SV = PV(0x8bcdb00) at 0x8bcd75c
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x8bee7d0 "five"\0
  CUR = 4
  LEN = 8
[download]

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}