perldoc -f fork

It returns the child pid to the parent process, 0 to the child process, or "undef" if the fork is unsuccessful.

When you compare undefined $pid with any number you get warning

You can make something like this: die "Can't fork: $!" unless defined $pid;

In reply to Re: Uninitialized value in numeric eq (==) after 65 iteration of a loop using fork?!? by ccn
in thread Uninitialized value in numeric eq (==) after 65 iteration of a loop using fork?!? by doowah2004

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