IO except handling

gistfile1.txt

scala> import scalaz._, Scalaz._, effects._
import scalaz._
import Scalaz._
import effects._

scala> val hello = putStrLn("Hello")
hello: scalaz.effects.IO[Unit] = scalaz.effects.IO$$anon$2@401c1b5f

scala> val bad:IO[Unit] = throwIO(new Exception("bad thing"))
bad: scalaz.effects.IO[Unit] = scalaz.effects.IO$$anon$2@1d296aa3

scala> val by = putStrLn("Goodbye")
by: scalaz.effects.IO[Unit] = scalaz.effects.IO$$anon$2@7147036a

scala> hello >|> bad  >|> by except (e => putStrLn(e.getMessage)) unsafePerformIO
Hello
java.lang.Exception: bad thing
        at .<init>(<console>:16)
        at .<clinit>(<console>)
        at .<init>(<console>:11)
        at .<clinit>(<console>)
        at $print(<console>)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:616)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)
        at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:914)
        at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:546)
        at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:577)
        at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:543)
        at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:694)
        at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:745)
        at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:651)
        at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:542)
        at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:550)
        at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:822)
        at scala.tools.nsc.interpreter.ILoop.main(ILoop.scala:851)
        at xsbt.ConsoleInterface.run(ConsoleInterface.scala:51)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:616)
        at sbt.compiler.AnalyzingCompiler.call(AnalyzingCompiler.scala:57)
        at sbt.compiler.AnalyzingCompiler.console(AnalyzingCompiler.scala:48)
        at sbt.Console.console0$1(Console.scala:23)
        at sbt.Console$$anonfun$apply$2$$anonfun$apply$1.apply$mcV$sp(Console.scala:24)
        at sbt.TrapExit$.executeMain$1(TrapExit.scala:33)
        at sbt.TrapExit$$anon$1.run(TrapExit.scala:42)