OK....I tried to give the simple example in the first post.. I thought I would explain what I am trying do in my code and what i want from it. Its true that 'do add.pl' didn't work at first but during this time I solved the problem.
from beginning...
1. I am creating a thread
2. In the thread I called a function.
3. In the called function there is expression to load
external perl file add.pl
4. The add.pl has network modules in it.
(Example: use Device::Modem::GSM)
Because of these modules the thread is ending abnormally.
This where I am facing the present problem.....
(Moreover I am not able format my post here)