You have 
               -X->+---------+
               -Y->| Node    |
               -Z->+---------+
                      |   ^
                      A   B
                      v   |
                   +---------+
                   | Node    |
                   +---------+

[download]

Your initial solution was to weaken "X", "Y" and "Z". That doesn't work because the creation of "Y" and "Z" is done outside of your control. You could weaken "B" instead. If for some reason, you can't do that (e.g. if you don't actually control the creation of those nodes), you could use a wrapper. 

-X->+---------+    +---------+
-Y->| Wrapper |-J->| Node    |
-Z->+---------+    +---------+
                      |   ^
                      A   B
                      v   |
                   +---------+
                   | Node    |
                   +---------+

[download]
The wrapper would has a destructor that deletes "A" or "B", breaking the loop, freeing the nodes. This wrapper has already been written for you: Object::Destroyer. 
use Object::Destroyer qw( );
$tree = Object::Destroyer->new($tree);

[download]

In reply to Re: return weak reference by ikegami
in thread return weak reference by flipper

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.