hash_of_arrays.rb

#!/usr/bin/env ruby

# define hash
hash = {
        "k1" => "v1",
        "k2" => ["v2","v3","v4"],
        "k3" => ["v5"],
}

puts hash

# print key/value pairs
hash.each do |key, value|
        if value.kind_of?(Array) 
                value.each { |inner_value| puts "#{key}:#{inner_value}" }
        else # not an array
                puts "#{key}:#{value}"
        end
end