Perl test measurement

gistfile1.pl

#!/usr/bin/env perl
use strict;
use warnings;
# use integer;


sub get_primes7 {
    my $n = shift;

    if ($n < 2) { return (); }
    if ($n == 2) { return (2); }

    my @s;
    push @s, $_*2 + 1 for 1..$n/2;

    my $mroot = $n ** 0.5;
    my $half = scalar @s;
    my $i = 0;
    my $m = 3;
    while ($m <= $mroot) {
        if ($s[$i]) {
            my $j = ($m*$m - 3) / 2;
            $s[$j] = 0;
            while ($j < $half) {
                $s[$j] = 0;
                $j += $m;
            }
        }
        $i = $i + 1;
        $m = 2*$i + 3;
    }

    return [2, grep {$_ != 0} @s];
}

my $res;
for (1..10) {
    $res = get_primes7(10000000);
    print "Found " . scalar @$res . " prime numbers.\n";
}

__END__

$ /usr/bin/time ./math_test.pl
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
Found 664579 prime numbers.
37.87user 0.15system 0:38.02elapsed 99%CPU
with 'use integer':
34.31user 0.13system 0:34.46elapsed 99%CPU