How can I create an anonymous hash from an existing hash in Perl?

Question

How can I create an anonymous hash from an existing hash?

For arrays, I use:

@x = (1, 2, 3);
my $y = [@x];

but I can't find how to do the same for a hash:

my %x = ();
my $y = ???;

Thanks

Answer 1

Why do you need an anonymous hash? Although the answers tell you various ways you could make an anonymous hash, we have no idea if any of them are the right solution for whatever you are trying to do.

If you want a distinct copy that you can modify without disturbing the original data, use dclone from Storable, which comes with Perl. It creates a deep copy of your data structure:

use Storable qw(dclone);
my $clone = dclone \%hash;

Consider Dave Webb's answer, but with an additional layer of references. The value for the key of c is another hash reference:

use Data::Dumper;

my %original = ( a => 1, b => 2, c => { d => 1 } );
my $copy = { %original };

print 
    "Before change:\n\n",
    Data::Dumper->Dump( [ \%original], [ qw(*original) ] ),
    Data::Dumper->Dump( [ $copy ], [ qw(copy) ] ),
    ;

$copy->{c}{d} = 'foo';

print 
    "\n\nAfter change:\n\n",
    Data::Dumper->Dump( [ \%original], [ qw(*original) ] ),
    Data::Dumper->Dump( [ $copy ], [ qw(copy) ] ),
    ;

By inspecting the output, you see that even though you have an anonymous hash, it's still linked to the original:

Before change:

%original = (
              'c' => {
                       'd' => 1
                     },
              'a' => 1,
              'b' => 2
            );
$copy = {
          'c' => {
                   'd' => 1
                 },
          'a' => 1,
          'b' => 2
        };


After change:

%original = (
              'c' => {
                       'd' => 'foo'
                     },
              'a' => 1,
              'b' => 2
            );
$copy = {
          'c' => {
                   'd' => 'foo'
                 },
          'a' => 1,
          'b' => 2
        };