The normal reference operator \ works just fine for elements of aggregates.

use Data::Dumper qw( Dumper );
my @a = ( 1, 2, 3, 4 );
print Dumper( \@a );
$x = \$a[2];
$$x = 9;
print Dumper( \@a );
exit 0;
__END__
$VAR1 = [
          1,
          2,
          3,
          4
        ];
$VAR1 = [
          1,
          2,
          9,
          4
        ];
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