I prefer to counteract these potential bugs by locking the keys of a hash. For eg. in Perl: use Hash::Util 'lock_keys'; my %hash = (key1 => 'foo', key2 =

I prefer to counteract these potential bugs by locking the keys of a hash. For eg. in Perl: use Hash::Util 'lock_keys'; my %hash = (key1 => 'foo', key2 => 'bar', key3 => 'baz'); lock_keys %hash; Now any attempts to lookup or amend a key that doesn't exist produces a runtime error... $hash{key1} = "FOO"; # updates fine $hash{key4} = "XXX"; # throws error