Oops..here is the output I am getting if I use perl 5.8.2.

My PID is 24958
My PPID is 24958 after my parent is killed
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It is probably returning the cached value of Parent PID.

But it works as expected if I use perl 5.6.1

My PID is 25020
My PPID is 1 after my parent is killed
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My OS info :
Linux version 2.4.21-4.ELsmp (bhcompile@daffy.perf.redhat.com) (gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-20)) #1 SMP Fri Oct 3 17:52:56 EDT 2003

Thanks,
Pratik