the $_ inside the grep is an alias of the hash-values, i.e. any assignment would be mirrored. For reasons that I don't understand yet (under-coffeination perhaps) this triggers an autovivification.

My educated guess is that it's because autovivification generally happens in an lvalue context.

In reply to Re^2: unexpected modify hash in a distance with grep { $_ } by haukex
in thread unexpected modify hash in a distance with grep { $_ } by leszekdubiel

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