I think the problem is that the %h you are referencing is gone (it's pad) before val is called. changing new to have a new copy of %h and fixing val to end with a a reference fixes it.
update
It does fix it but not because of garbage collection. See answer in reply below. 
#!/usr/bin/perl -w

use strict;
use Data::Dumper;

{
    package foo;
    use Tie::IxHash;
    use Data::Dumper;
    tie(my %h, 'Tie::IxHash', qw(one two three four));
    sub new { my %newh = %h; bless { val => \%newh } }
    sub val : lvalue  { my $r = \$_[0]->{val}{one}; $$r }
}

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

[download]


-Lee

"To be civilized is to deny one's nature."

In reply to Re: lvalue trickery solution by shotgunefx
in thread lvalue trickery by broquaint

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.