in reply to I am not able to join a thread when another child process is running which was forked using open.
from perlthrtut:
Thinking of mixing "fork()" and threads? Please lie down and wait until the feeling passes. Be aware that the semantics of "fork()" vary between platforms. For example, some UNIX systems copy all the current threads into the child process, while others only copy the thread that called "fork()". You have been warned!
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Seekers of Perl Wisdom