The Mathematica Clipboard window can evaluate multiple lines of code at a time. When multiple lines are evaluated on the Clipboard, only the result from the last line is returned. You can use this behavior to progressively build up code that can be used as a macro by alternatively clicking Evaluate and Restore.
Developing code on the Clipboard.
When used this way, the Mathematica Clipboard window becomes a floating macro code box. The Clipboard Evaluate button becomes a Run button for the macro during development. When you are done developing, you can transfer the code to a code box.
To transfer code from the Mathematica Clipboard to a code box:
Paste.