Working with regular expressions was never my favorite task as a developer (and it still isn't). The syntax is arcane and when you come back to them after a while it takes a great deal of effort to figure out how they work. With ReEX you can experiment with regular expressions wherever and whenever it is convenient, not just in front of the computer screen. ReEX allows you to test any expression you enter with data you enter manually or paste into the input area. It will also tell you if the expression you entered is valid or not. Invalid expressions are indicated in red.