```{index} single: lock_ref_keys; Hash::Util function ``` ```{index} single: Hash::Util::lock_ref_keys; Perl function ``` # lock_ref_keys Hash-reference variant of `lock_keys`. ## Synopsis lock_ref_keys($href); lock_ref_keys($href, @keys); Exactly the same effect as `lock_keys`, but takes an already-taken hash reference rather than relying on the `\%` prototype. Useful when the hash only exists as a reference — for example, an anonymous hash or a field on an object.