If Perl finds something in the command line for exec or system that it can't interpret (like a redirection), it will invoke the shell to parse the command. This is what's happening here.

As a solution, you could either do the redirect yourself by reopening STDERR to the file or restructure your approach so that you get the correct PID into the appropriate place.

In reply to Re^2: getting a child's process ID by Corion
in thread getting a child's process ID by Seshouan

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