Answer to number 3: run (under windows)

perldoc Benchmark
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to read the POD for the module. If you have a somewhat old and/or broken install (like me), you can always fall back to

vi \perl\lib\Benchmark.pm
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:)

What you've written is a proper way of using benchmark. Ideally, you would insert several objects into your code to get the times you wanted, but you can do it in a clever and inobtrusive manner:

BEGIN {
   use Benchmark;
   my ($oldb, $newb);    # inside BEGIN for closure

   sub mybench {
      return unless ($opt_b);

      $newb = new Benchmark;
      if ($oldb) {       # i.e. don't run first time through
          print timediff($oldb, $newb);
      }
      $oldb = $newb;
   }
}

Getopt::Std;

getopts('b');

mybench();
# some code here
mybench();
# some more code here
mybench();
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and then it would be trivial to remove the benchmarking from your production code, either through a command line switch, as above:

mycode.pl -b
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or some line in your makefile like:

perl -lne 'print unless /^\s*mybench();/' myscript.pl > production.pl
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ya know.