várias maneiras
"abcd"[-1..-1]
=> "d"ou
"abcd"[-1,1]
=> "d"ou
"abcd".slice(-1,1)
=> "d"ou
"abcd".slice(-1).chr
=> "d"ou
"abcd"[ /.$/ ]
=> "d"ou
"abcd".reverse[0,1]
=> "d"ou
"abcd".split('').pop
=> "d"ou
class String
def last
self[-1,1]
end
end
"abc".last
=> "d"