While the other respondants are correct that the using 
$check = Data::Dumper->new([$old],[qw(old)])->Purity(1)->Dump

[download]
Will at least give evalable results you should be cautious with self referential structures and D::D. Some structures are fundamentally undumpable with D::D (and most dumpers actually, D::BFDump tries to solve this, but i havent had time to fix some bugs so dont go there right now.)

But more pertinent (as i think its unlikely that you will be dumping such structures) is that as D::D does not sort the keys of a hash you can not rely on it dumping two (for all intents and purposes) identical hashes in exactly the same way. The keys may be output in any order and thus doing a string compare on the results is not a sufficient test to determine if the two structures are the same.

HTH

--- demerphq
my friends call me, usually because I'm late....

In reply to Re: evaling dumped cyclic structures by demerphq
in thread evaling dumped cyclic structures by marvell

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.