Ability to be able to write a small piece of code when stopped in debugger (in the current context/scope) and execute that code. This can typically come in handy especially when running in a loop and trying to access some specific members of some variables (toString might be too generic in this case).
This is a debugging code that you do not want to add to the code and also do not want to check out the file.
This is available in Visual Age for Java.
-- VinayMoharil - 20 Aug 2002