+ "undef" is returned when the expression would have autovivified.
+
+ * 'store'
+
+ Turns off autovivification for lvalue dereferencing expressions,
+ such as :
+
+ $arrayref->[$idx] = $value
+ $hashref->{$key} = $value
+ for ($arrayref->[$idx]) { ... }
+ for ($hashref->{$key}) { ... }
+ function($arrayref->[$idx])
+ function($hashref->{$key})
+
+ An exception is thrown if vivification is needed to store the value,
+ which means that effectively you can only assign to levels that are
+ already defined In the example, this would require $arrayref (resp.
+ $hashref) to already be an array (resp. hash) reference.
+
+ * 'warn'
+
+ Emits a warning when an autovivification is avoided.
+
+ * 'strict'
+
+ Throws an exception when an autovivification is avoided.
+
+ Each call to "unimport" adds the specified features to the ones already
+ in use in the current lexical scope.
+
+ When @opts is empty, it defaults to "qw<fetch exists delete>".
+
+ "import @opts"
+ Magically called when "use autovivification @opts" is encountered.
+ Disables the features given in @opts, which can be the same as for
+ "unimport".
+
+ Each call to "import" removes the specified features to the ones already
+ in use in the current lexical scope.
+
+ When @opts is empty, it defaults to restoring the original Perl
+ autovivification behaviour.
+
+CONSTANTS
+ "A_THREADSAFE"
+ True iff the module could have been built with thread-safety features
+ enabled. This constant only has a meaning with your perl is threaded ;
+ otherwise, it'll always be false.
+
+ "A_FORKSAFE"
+ True iff this module could have been built with fork-safety features
+ enabled. This will always be true except on Windows where it's false for
+ perl 5.10.0 and below .
+
+CAVEATS
+ The pragma doesn't apply when one dereferences the returned value of an
+ array or hash slice, as in "@array[$id]->{member}" or
+ @hash{$key}->{member}. This syntax is valid Perl, yet it's discouraged
+ as the slice is here useless since the dereferencing enforces scalar
+ context. If warnings are turned on, Perl will complain about one-element
+ slices.