I have just discovered that the issue is with having two perl modules with the same name but in different directories.
i.e
/u01/my_app/my_app_perl_libs/my_app_util.pm
and
/u01/my_app8/my_app_perl_libs/my_app_util.pm

As soon as I comment out the my_app8 virtual host entry the erros do no occur. This means that these two perl utils are conflicting with each other.
Changing their name is not feasible as many perl scripts are dependent.

Still looking for a good solution.

Thanks,
Rahul.