how to know which regression should i use code example

Example: how do you check regression

First, I have to execute my script.
Once the script execution is completed,
I have to analyze the run result to see if there is
any failed test cases. If there is 
failed test cases I have to determine 
if it is failed due to legitimate
application issue or it is
caused by some script issue.
(the script can be failed due to automation code issue too)
if it is caused by application issue,
I will try to manually reproduce it 
and log a defect if I can reproduce.
If it is due to my script, I have to fix it. But this is not
the case most of the time.