in reply to Can a hash self reference?
For what it's worth, self-reference is more commonly called circular reference. Objects with circular references need some guidance about how they should be garbage collected; it doesn't happen automatically. There is a very good discussion of this at Proxy Objects:
Building Garbage Collected Circular References which also touches on what makes references circular in general, and how you can dissect them using devel::peek and other tools. Good luck!
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