New repl feature: you can start a line with .

on the previous result.  For instance:

  scala> (1 to 10).iterator
  res0: Iterator[Int] = non-empty iterator

  scala> .toList.sum
  res1: Int = 55

2 files changed, 22 insertions, 4 deletions

diff --git a/src/compiler/scala/tools/nsc/Interpreter.scala b/src/compiler/scala/tools/nsc/Interpreter.scala
index 1655c0130d..1185600c94 100644
--- a/src/compiler/scala/tools/nsc/Interpreter.scala
+++ b/src/compiler/scala/tools/nsc/Interpreter.scala
@@ -185,12 +185,17 @@ class Interpreter(val settings: Settings, out: PrintWriter)
   /** Generates names pre0, pre1, etc. via calls to apply method */
   class NameCreator(pre: String) {
     private var x = -1
+    var mostRecent: String = null
+
     def apply(): String = {
       x += 1
       val name = pre + x.toString
       // make sure we don't overwrite their unwisely named res3 etc.
-      if (allBoundNames exists (_.toString == name)) apply()
-      else name
+      mostRecent =
+        if (allBoundNames exists (_.toString == name)) apply()
+        else name
+
+      mostRecent
     }
     def reset(): Unit = x = -1
     def didGenerate(name: String) =
@@ -868,6 +873,18 @@ class Interpreter(val settings: Settings, out: PrintWriter)
     }
   }
 
+  /** Returns the name of the most recent interpreter result.
+   *  Mostly this exists so you can conveniently invoke methods on
+   *  the previous result.
+   */
+  def mostRecentVar: String =
+    prevRequests.last.handlers.last.member match {
+      case x: ValOrDefDef           => x.name
+      case Assign(Ident(name), _)   => name
+      case ModuleDef(_, name, _)    => name
+      case _                        => varNameCreator.mostRecent
+    }
+
   private def requestForName(name: Name): Option[Request] = {
     for (req <- prevRequests.toList.reverse) {
       if (req.handlers.exists(_.boundNames contains name))
diff --git a/src/compiler/scala/tools/nsc/InterpreterLoop.scala b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
index 2b926d8e80..0f68f8fc5a 100644
--- a/src/compiler/scala/tools/nsc/InterpreterLoop.scala
+++ b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
@@ -342,7 +342,7 @@ class InterpreterLoop(in0: Option[BufferedReader], out: PrintWriter) {
 
   def power() {
     powerUserOn = true
-    interpreter.powerUser()
+    out println interpreter.powerUser()
     interpreter.quietBind("history", "scala.collection.immutable.List[String]", historyList.toList)
   }
 
@@ -387,7 +387,8 @@ class InterpreterLoop(in0: Option[BufferedReader], out: PrintWriter) {
     * to be recorded for replay, if any.
     */
   def interpretStartingWith(code: String): Option[String] =
-    interpreter.interpret(code) match {
+    if (code startsWith ".") interpretStartingWith(interpreter.mostRecentVar + code)
+    else interpreter.interpret(code) match {
       case IR.Error       => None
       case IR.Success     => Some(code)
       case IR.Incomplete  =>