>> RUBY_DESCRIPTION
=> "ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin11.3.0]"
>> a = %w(a b c d e f g)
=> ["a", "b", "c", "d", "e", "f", "g"]
>> Hash[a.map{|x|[x,true]}]
=> {"a"=>true, "b"=>true, "c"=>true, "d"=>true, "e"=>true, "f"=>true, "g"=>true}