I am sorry for the late reply. Thanks for the help Kyle and TGI. I think the best solution can be achieved only through means of test suite that covers the code comprehensively as mentioned in Re: Cleaning up unused subroutines, since Perl code can have dynamic method calls and I am not sure if it is possible to determine through script.

But as of now I am working on a solution for finding the subroutines that contains the session directly and then also find other subroutines that call the first list of subroutines. Finally analyse the code for the remaining subroutines and also filter them. However, need to get the better solution(using code coverage) in the long run. Also couldn't do much using PPI as I didn't know how to catch the method calls using it. I will have to work on that too later!
Thanks,
Ganesh