On perl's side, closing the file handle flushes the data and releases the process (does a waitpid).

On sort's side, the closed input tells sort it's done receiving data so it can proceed to sort and print it.

In reply to Re^2: Is it possible to use the open( ) function with piped unix commands? by ikegami
in thread Is it possible to use the open( ) function with piped unix commands? by shaolin

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