{
    package foo;
    # not tied so all is well
    my %h = qw(one two three four);

    sub new { bless { val => \%h } }
    sub val : lvalue  { $_[0]->{val}->{one} }
}

use Devel::Peek;
my $obj =  foo->new;
$obj->val = "foo";
Dump( $obj->{val}->{one} );

__output__

SV = PV(0x80f9c40) at 0x80f9964
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x80f9018 "foo"\0
  CUR = 3
  LEN = 4

##</code><code>##

{
    package foo;
    use Tie::IxHash;
    tie(my %h, 'Tie::IxHash', qw(one two three four));

    sub new { bless { val => \%h } }
    sub val : lvalue  { $_[0]->{val}->{one} }
}
use Devel::Peek;
my $obj =  foo->new;
Dump( $obj->{val}->{one} );
#  dies here
$obj->val = "foo";

__output__
SV = PVMG(0x8131170) at 0x8154b68
  REFCNT = 1
  FLAGS = (TEMP,GMG,SMG,RMG)
  IV = 0
  NV = 0
  PV = 0
...  many more lines of output

Can't return a temporary from lvalue subroutine at - line 9