For future reference on Kleisli

kleisli.scala

import scalaz._
import Scalaz._
import scala.concurrent.Future
import scalaz.std.scalaFuture._
import play.api.libs.concurrent.Execution.Implicits._

val f1 = (s: String) => Option("foo").point[Future]
def f2 = (s: String) => Option(1).point[Future]

type OptionTFuture[T] = OptionT[Future, T]

for {
  e1 <- Kleisli(f1).mapK[OptionTFuture, String](OptionT.apply _)
  e2 <- Kleisli(f2).mapK[OptionTFuture, Int](OptionT.apply _)
} yield e1 + e2