- as "$value = $hashref->{key}[$idx]{$field}". "undef" is returned
- when the expression would have autovivified.
+ as "$value = $hashref->{key}[$idx]{$field}", "keys
+ %{$hashref->{key}}" or "values %{$hashref->{key}}". When the
+ expression would have autovivified, "undef" is returned for a plain
+ fetch, while "keys" and "values" return 0 in scalar context and the
+ empty list in list context.