open(STDOUT, "/dev/null");          # suppressing output  
open(STDERR, "/dev/null");          # suppressing output
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Yes, this suppresses output, but accidentally. You open STDOUT and STDERR for input. That may confuse your child process. What you really want is the three-argument form of open, used for output:

open STDOUT,'>','/dev/null';
open STDERR,'>','/dev/null';
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Alexander