Type in expressions to have them evaluated.
Type :help for more information.

scala> :silent
Switched off result printing.

scala> class A { override def toString() = { println("!"); "A" } }

scala> val a = new A

scala> var b: A = new A

scala> b = new A

scala> new A

scala> :silent
Switched on result printing.

scala> res0
!
res1: A = A

scala> :quit