To play with Kotlin's REPL, you can type the following:

$ kotlinc

Now you can type and execute Kotlin expressions:

$ kotlinc
Welcome to Kotlin version 1.2.21 (JRE 1.8.0_111-b14)
Type :help for help, :quit for quit
>>> println("Hello, World!")
Hello, World!
>>> 

To exit Kotlin's REPL, you can type :quit