In SSIS 2012, We can write expressions while creating the variable and we do not have to go to properties windows. The Description can also be provided. Once expression are written and evaluated , the EvaluateAsExpression property get set to True automatically as well.
|In SSIS 2008, no Description and Expression button was available|
SSIS 2012 New Variable Pane
|Description and Expression Tabs in SSIS Package|
|How to write expression on Variable by using Expression Tab in SSIS Package|