As chipmunk pointed out the structure _is_ self-referencing from the point of view of dumper. Dumper is simply reusing the first 'undef' it encounters. (Very annoying, I know.)

Also, IMO when using Dumper one should _always_ set Purity to be true

use Data::Dumper;
$Data::Dumper::Purity=1;
[download]

Its suprising the different results that can occur.

Yves / DeMerphq
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When to use Prototypes?