Let's say you have the following hash. In this example, the employee_key in the hash is empty.

my %hash = ( 'employee_key' => '' );

You can count the elements.

my $keys   = keys %hash;
my $values = values %hash;
print "keys   = $keys \n";
print "values = $values \n";

Which will return 0, since employees_key is empty.

keys = 0
values = 0

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

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

Which should produce the following.

$VAR1 = {
          'employees_key' => ''
        };

A value can be appended to employee_key, like this.

$hash{"employee_key"} = "John Doe";

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

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

Now, employe_ key contains a value of John Doe.

$VAR1 = {
           'employee_key' => 'John Doe'
        };

Multidimensional

In this example, name_key is below employee_key.

my %hash = ( 'employee_key' => { 'name_key' => '' } );

A value can be appended to name_key, like this.

$hash{employee_key}->{name_key} = "John Doe";

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

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

Now, name_key contains a value of John Doe.

$VAR1 = {
           'employee_key' => {
                               'name_key' => 'John Doe'
                             }
            };