Empty hash

Let's say you have the following empty hash that contains no keys and no values.

my %hash;

The following can be used to print the number of keys and values in the hash.

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

Which should return the following.

keys = 0
values = 0

Hash with keys and values

Let's append some keys and values. In this example, the hash has three keys (employee_key, id_key, department_key) and three values (John Doe, 123456, Engineering)

my %hash;
$hash{employee_key}   = "John Doe";
$hash{id_key}         = "123456";
$hash{department_key} = "Engineering";

Print the number of keys and values in the hash.

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

Which should return the following.

keys = 3
values = 3

Empty hash array

In this example, employees_key is an empty array, as indicated by the [ ] characters.

my %hash = ( 'employees_key' => [] );

Print the count of the array.

my $count = @{$hash{employees_key}};
print "count = $count \n";

Which should return the following.

count = 0

Non-empty Hash array

Let's say you do this. Now the hash array contains two child keys (name_key and department_key).

push @{$hash{employees_key}}, { 'name_key' => 'John Doe', 'department_key' => 'engineering' };

Print the count of the array.

my $count = @{$hash{employees_key}};
print "count = $count \n";

Which should return the following.

count = 1

Child keys

The following can be used to print the number of child keys in the hash.

foreach my $employees_key (@{$hash{employees_key}}) {
  my $count = keys %$employees_key;
  print "$count \n";
}

Which should return the following.

2