When you have program data that must be fed as the standard input to a process, and you want to capture its output, and you want to avoid the shell, it's time for a double fork!
my @INPUT = (... many lines of text ...);
my @COMMAND = qw(tr a-zA-Z A-Za-z); # swap lower/upper case
my @RESULT; # this is where the result will go...
if (open RESULT, "-|") { # original process
  @RESULT = <RESULT>;
} else { # child
  if (open STDIN, "-|") { # child
    exec @COMMAND;
    die "Cannot exec: $!";
  } else { # grandchild
    print @INPUT;
    exit 0;
  }
}

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In reply to feeding text to a process, and capturing its output, safely by merlyn

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