Actually, I'm a bit surprised that I do get the same warning with a slightly modified variant: 

$ perl -Mstrict -Mwarnings -MData::Dumper -le 'my $hr; $hr->{stuff}{fo
+o} for 1; print Dumper $hr'
Useless use of hash element in void context at -e line 1.
$VAR1 = {
          'stuff' => {}
        };

[download]

As it autovivifies, it's not "useless", strictly speaking...  Also, what about (intended) side effects with tied hashes?

In reply to Re^2: Possible useless use of map by almut
in thread Possible useless use of map by andreas1234567

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