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....