ptoulis's comment about stack-oriented loop structures got me thinking. What if the inner loop were replaced with individual lines of code? Here's what I came up with: 
sub new {
    my $i = 0;
    while ($i += 20) {
        next if ($i % 1);
        next if ($i % 2);
        next if ($i % 3);
        next if ($i % 4);
        next if ($i % 5);
        next if ($i % 6);
        next if ($i % 7);
        next if ($i % 8);
        next if ($i % 9);
        next if ($i % 10);
        next if ($i % 11);
        next if ($i % 12);
        next if ($i % 13);
        next if ($i % 14);
        next if ($i % 15);
        next if ($i % 16);
        next if ($i % 17);
        next if ($i % 18);
        next if ($i % 19);
        print "Number: $i\n"; last;
    }
}

[download]
Then I benchmarked it against your original Perl code and got these results: 
         s/iter original      new
original   25.7       --     -63%
new        9.57     168%       --

[download]
Admittedly, it doesn't scale very well and this example is very case specific, but I'll be paying closer attention to where and how I use loops from now on.

In reply to Re: Why is this code so much slower than the same algorithm in C? by ruzam
in thread Why is this code so much slower than the same algorithm in C? by wanna_code_perl

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