Sorry all, can't share code.
As far exit in the code is concerned. I am not calling exit at all.
Subroutine is only return 1 for Success and 0 for false.
I have put <> in my main code and still observed the same behavior.
I have used http://www.xav.com/perl/lib/Pod/perlthrtut.html to understand how Perl Threads work. Is there any other website with more details?