hash.rb

#!/usr/bin/env ruby

require 'yaml'

bar = [ { 'key1a' => 'value1_0', 'key1b' => 'value1_1' },
          'key2',
          'key3',
          { 'key4a' => 'value4_0', 'key4b' => 'value4_1' }
      ]

puts bar[0]['key1a']

puts bar.to_yaml

hash.rb.txt

value1_0
---
- key1a: value1_0
  key1b: value1_1
- key2
- key3
- key4a: value4_0
  key4b: value4_1

init.pp

include foo

class foo {
        $bar = { 'key1' => 'value_a',
                'key2' => [ 'value_b_0', 'value_b_1' ] }
         notice("hi ${foo::bar['key1']} ${foo::bar['key2'][0]}")
}