"Premature optimisation is the root of all evil." -- Donald Knuth

Knuth's famous quotation applies to many of these constructs. Especially as readability is often never included in such benchmarks :). I was glad to see your warning at the top of the quiz but I thought I'd add my own.

Question 9-10 in particular can be very misleading; especially given that you don't show your method. As it's showing a counting loop, instead of an array iteration loop, it could easily trap the unwary. See Efficient Looping Constructs for some good discussion on this.

I'm also a little inclined to question your methodology. Are you using subs with lexicals to make sure they don't have any interaction with each other? I'm not saying you're doing anything wrong, just some of these results suprised me and don't compare with my benchmarks. This could just be differences in our approach and choice of test strings.

As a side note, consider for ($i=1; $i < $n+1; $i++). You're doing an extra assignment in there every loop. That slows it down considerably for ($i=1; $i <= $n; $i++) is quite a bit faster (and clearer IMO, though not as clear as Perl-ish for). Seeing a foreach along the lines of for my $i (1..$n) might have been nice too, and the results might suprise you :).

Counting loops have already been covered, but I can't seem to find a good node comparing C style for(;;) loops against Perl style foreach when iterating over lists/arrays (probably their most common usage). So read on if you want a quick benchmark.

#!/usr/bin/perl -w
use strict;
use Benchmark qw(cmpthese);

# Yes I do want it to be 5000 if $ARGV[0] is 0 ;)
my $n = $ARGV[0] || 5000;

# Grab a chunk of memory and give it to perl.
my @array = (1..50000);
undef @array;

cmpthese(-10, {
    a => "&a($n)",
    b => "&b($n)",
    c => "&c($n)",
    d => "&d($n)",
});

sub a {
    my @a = (1..shift);
    my $m;
    
    for ( @a ) {
        $m = $_;
    };
}

sub b {
    my @a = (1..shift);
    my $m;

    for my $i ( @a ){
        $m = $i
    };
}


sub c {
    my @a = (1..shift);
    my $m;

    $m = $_ for ( @a );
}


sub d {
    my @a = (1..shift);
    my $m;

    for (my $i=0; $i <= $#a; $i++) {
        $m = $a[$i];
    };
}
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