But you are not measuring what you think you are! Once again, the high number of iterations per second Benchmark is reporting should ring many bells and whistles. Do you really think your computer is able to do more than 3 billion modulus operations per second? Because if you believe your Benchmark results, it's grepping through a 1000001 element array 315978.92 times a second. Of course it isn't. You have my @array, which makes that @array is only visible from the file. And not from an eval that's happening in Benchmark.pm (that would defeat all the purposes of my, wouldn't it?), Changing the last lines to:

our @array = (0..1000000);

timethese(-10, {
  'Step 1' => 'step1(500000, @::array)',
  'Step 2' => 'step2(500000, @::array)',
  'Step 3' => 'step3(500000, @::array)'
});
[download]

we get far more sensible results:

Benchmark: running Step 1, Step 2, Step 3 for at least 10 CPU seconds.
+..
  Step 1: 10 wallclock secs (10.17 usr +  0.00 sys = 10.17 CPU) @  5.1
+1/s (n=52)
  Step 2: 10 wallclock secs (10.00 usr +  0.00 sys = 10.00 CPU) @  5.1
+0/s (n=51)
  Step 3: 11 wallclock secs (10.72 usr +  0.00 sys = 10.72 CPU) @  0.4
+7/s (n=5)
[download]

Two things can be learned. First, don't blindly use my. Think whether it's appropriate. Second, always distrust your code if Benchmark returns many iterations per second - especially if you do lots of work during an iteration.

Abigail