module MyModule
  chars = %w(A B C)
  words = chars.permutation.to_a
  
  words.each do |word|
    method_name = word.join
    module_eval(<<-PERMUTATION, __FILE__, __LINE__)
      def #{method_name}
        puts "#{word}"
      end
    PERMUTATION
  end
end

include MyModule

abc  # => nil
# >> a
# >> b
# >> c