There are CPAN modules that make hashes non-modifiable, like Readonly.

Maybe $u is such a read-only hash? Or a tied hash that doesn't support modification?

It would help if you could provide a small sample that lets us reproduce the problem.

In reply to Re: Modification of non-creatable hash value attempted by moritz
in thread Modification of non-creatable hash value attempted by dgaramond2

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