'purport'! You are suggesting that I'm not testing?

No. I should have said: "That your benchmark purports to be testing". (Where 'your' refered to ikegami). The point is that it looks like it's testing the right thing, but when you factor in the overhead of the tests, it serves to completely obscure the results.

Like others, I think this is a fairly fruitless test. If you are doing this once, then the method used will make very little difference. If you are doing it hundreds of thousands of times, then there are far more efficient ways of doing it. For example,

1. if the idea is to chip off characters until you reach a particular character, then search for the character and then chop the lump off:

   ## Either
   substr( $x, 0, index( $x, $char ), '');
   ## or
   $x =~ s[(^/*$char)][];
   [download]

2. if the requirement is to remove and process the first N chars of a string, then chop off the lump then separate them:

   for my $char ( unpack '(A1)*', substr $x, 0, 100, '' ) {
       ##
   }
   [download]

The only time the relative performance of these methods is likely to make a significant difference is if you were applying it once to each of a large number of strings, say a large array, much as you might with chop( @array ). And it would have to be in the order of 10e7 elements before it would have any significant effect upon an application. If it was a common requrement, then there would probably be a leading character equivalent of chop (chip()?:) built-in.

Could you give an example of 'add a multiplier loop inside the subroutine'?

This was how I constructed my variation:

use strict;
use warnings;

use Benchmark qw( cmpthese );

my %tests = (
   subst       => '$x =~ s/.//;',
   substr_lval => 'substr($x,0,1) = "";',
   substr_mod  => 'substr($x,0,1,"");',
   reverse     => '$x = reverse $x; chop($x); $x = reverse($x);',
   substr_copy => '$x = substr($x,1);',
);

our $loops ||= 1e4;
for (values %tests) {
    $_ = <<EOT
    my \$x = 'X' x $loops;
    for( 1 .. $loops ) {
       $_
    }
EOT

}

cmpthese(-3, \%tests);
[download]