lock_keys

Restrict a hash to its current keys, or to an explicit list.

Synopsis

lock_keys(%hash); # pin the current keyset lock_keys(%hash, @keys); # pin to the given keyset

With one argument, subsequent attempts to assign to a key not already in %hash croak with Attempt to access disallowed key '...' in a restricted hash. With more arguments, the extra keys specify the allowed set; existing keys that do not appear in that set make the call croak with Hash has key '...' which is not in the new key set. Keys in the allowed set that are not yet present are accepted later (their slots start as hidden placeholders).

delete and exists still work on a locked hash and do not change the legal keyset — a deleted key can be reassigned, but a brand-new key still cannot. Returns a reference to the hash.

A locked hash cannot be blessed; bless before locking if you need both.