Lot of people know about Regular Expression but do not use them when required. This is because it's more complex and time comsuming to write at begging. But when you mast the underlying comcepts, it's all done.
Here are some good links that you can use in day to day life of a programmer.
- If you are using firefox browser this extension is for you: https://addons.mozilla.org/firefox/2077/
- Regular expression Tester: http://www.regextester.com/
- This is online tester for regular expression. It accepts more than one input and validated results immediately in result window as you change you expression. This is my favorite for writing regular expression.