no autovivification;
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is short for

no autovivification qw( fetch exists delete );
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However, the list values of the foreach loop is evaluated in lvalue context so the loop body can alter (store values into) the resulting variables.

$_ = uc($_) for @a;
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As such, you need

no autovivification qw( fetch exists delete store );
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$ perl -e'
   use Data::Dumper;

   {
      no autovivification qw( fetch exists delete );
      my $h;
      for (@{ $h->{k} }) { }
      print(Dumper($h));
   }

   {
      no autovivification qw( fetch exists delete store );
      my $h;
      for (@{ $h->{k} }) { }
      print(Dumper($h));
   }
'
$VAR1 = {
          'k' => []
        };
Can't vivify reference at a.pl line 14.
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