In Perl, there are 2 different kinds of hashes.

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

Let's say you define a hash array named %hash that contains a single key (foo). The foo key will contain an array of values. The [ ] characters are used to set the foo key as an array.

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

The following can be used to print the number of values in the foo key.

my $count = values $hash{foo};
print "values = $count \n";

Which should return the following.

values = 0

Let's say the foo key contains 2 values.

my %hash = ( 'foo' => [ 'John Doe', 'Jane Doe' ] );

Now, the following should be returned.

values = 2