Hi Sid,
The best method to figuring out the exact pattern for your use case, is using an online regex tester.
In the above regex, its looking for \r Carriage return character, \n Line feed character, \t Tab character.
Excerpt from "Regular Expressions Quick Start ":
the vertical bar or pipe symbol |, the question mark ?, the asterisk or star *, the plus sign +, the opening parenthesis (, the closing parenthesis ), the opening square bracket [, and the opening curly brace {. These special characters are often called "metacharacters". Most of them are errors when used alone.
Regex Quick Reference for understanding the switches:
http://www.regular-expressions.info/refquick.html