In Perl, there are 3 different kinds of hashes.

• A regular hash, which is defined by the % and ( ) characters - %hash = ( );
• A reference hash, which is defined with the $ and { } characters = $hash = { };
• A hash array, which is defined with the % and [ ] characters - %hash = [ ];

Let's say you have the following hash. In this example, the hash has two keys, foo and bar.

my %hash;
$hash{foo} = "Hello";
$hash{bar} = "World";

The following can be done to sort the keys alphabetically within the foreach loop.

This will not actually sort or modify the hash. This only sorts the keys as part of the foreach loop

foreach my $key (sort keys %hash) {
  print "$key \n";
}

Which should return the following.

bar
foo

Dumper can be used to display the structure of the hash.

use Data::Dumper;
print Dumper \%hash;

Which should return the following. In this example, the key's are not sorted alphabetically.

$VAR1 = {
           'foo' => 'Hello',
           'bar' => 'World'
        };

The following can be done to sort the keys alphabetically.

This will not actually sort or modify the hash. This only sorts the keys for the Dumper output.

$Data::Dumper::Sortkeys = sub { [ sort keys %hash ] };

Printing the hash . . .

print Dumper \%hash;

. . . should return the following. Now, the keys are sorted alphabetically.

$VAR1 = {
           'bar' => 'World',
           'foo' => 'Hello'
        };