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 = [ ];

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, id, department) and three values (John Doe, 123456, Engineering)

my %hash;
$hash{employee}   = "John Doe";
$hash{id}         = "123456";
$hash{department} = "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