Lock and unlock hash using Hash::Util

If you don't like the autovivification or simply would like to make sure the code does not accidentally alter a hash the Hash::Util module is for you.

You can lock_hash and later you can unlock_hash if you'd like to make some changes to it.

In this example you can see 3 different actions commented out. Each one would raise an exception if someone tries to call them on a locked hash. After we unlock the hash we can execute those actions again.

I tried this both in perl 5.40 and 5.42.

examples/locking_hash.pl

use strict;
use warnings;
use feature 'say';

use Hash::Util qw(lock_hash unlock_hash);
use Data::Dumper qw(Dumper);


my %person = (
    fname => "Foo",
    lname => "Bar",
);
lock_hash(%person);

print Dumper \%person;
print "$person{fname} $person{lname}\n";
say "fname exists ", exists $person{fname};
say "language exists ", exists $person{language};

# $person{fname} = "Peti";     # Modification of a read-only value attempted
# delete $person{lname};       # Attempt to delete readonly key 'lname' from a restricted hash
# $person{language} = "Perl";  # Attempt to access disallowed key 'language' in a restricted hash

unlock_hash(%person);

$person{fname} = "Peti";     # Modification of a read-only value attempted
delete $person{lname};       # Attempt to delete readonly key 'lname' from a restricted hash
$person{language} = "Perl";  # Attempt to access disallowed key 'language' in a restricted hash

print Dumper \%person;

$VAR1 = {
          'lname' => 'Bar',
          'fname' => 'Foo'
        };
Foo Bar
fname exists 1
language exists
$VAR1 = {
          'language' => 'Perl',
          'fname' => 'Peti'
        };