Regular expression is used when window name recorded in GUI file keeps on changeing, and if we know that first 2 characters will not change we can put a regular expression above those two characters and then that change of window name will not hang your script. Read more about it in Help. Also exceptions are used to handle some thing unexpected, for example we have a application working absolutely fine but we know we can get a run time error (common in VB applications) any time, so by using exception we can trap that error and restart our application to continue testing. Read more about win_pop_up exception its the most easiest way to understand exceptions.
There's a solution for every problem, it depends how quick you want it