perl5.8.8
             Rate    single   capture kramercap     trick    double
single     3596/s        --       -9%       -9%      -95%      -96%
capture    3946/s       10%        --       -0%      -94%      -95%
kramercap  3960/s       10%        0%        --      -94%      -95%
trick     71359/s     1884%     1708%     1702%        --      -11%
double    80563/s     2140%     1942%     1935%       13%        --
perl5.10.1
             Rate    single   capture kramercap     trick    double
single     1857/s        --      -50%      -51%      -98%      -98%
capture    3702/s       99%        --       -1%      -95%      -96%
kramercap  3756/s      102%        1%        --      -95%      -96%
trick     76323/s     4010%     1962%     1932%        --      -10%
double    85132/s     4485%     2200%     2167%       12%        --
perl5.11.5
             Rate    single   capture kramercap     trick    double
single     1820/s        --      -50%      -51%      -98%      -98%
capture    3657/s      101%        --       -1%      -95%      -96%
kramercap  3691/s      103%        1%        --      -95%      -96%
trick     75045/s     4024%     1952%     1933%        --      -11%
double    84148/s     4524%     2201%     2180%       12%        --
perl5.12.0
             Rate    single   capture kramercap     trick    double
single     1734/s        --      -50%      -50%      -98%      -98%
capture    3446/s       99%        --       -1%      -95%      -96%
kramercap  3466/s      100%        1%        --      -95%      -96%
trick     72542/s     4084%     2005%     1993%        --      -10%
double    80991/s     4572%     2250%     2237%       12%        --
perl5.12.1
             Rate    single   capture kramercap     trick    double
single     1749/s        --      -49%      -51%      -98%      -98%
capture    3455/s       98%        --       -2%      -95%      -96%
kramercap  3540/s      102%        2%        --      -95%      -96%
trick     74052/s     4134%     2044%     1992%        --      -10%
double    82732/s     4630%     2295%     2237%       12%        --
perl5.12.2
             Rate    single   capture kramercap     trick    double
single     1972/s        --      -50%      -51%      -97%      -97%
capture    3915/s       99%        --       -2%      -94%      -95%
kramercap  3998/s      103%        2%        --      -94%      -95%
trick     64740/s     3183%     1554%     1519%        --      -11%
double    73100/s     3607%     1767%     1728%       13%        --

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw(:all);

my $a = 'a' x 1_000;

my @x = (
         "    $a   ",
         "$a   ",
         $a,
         "    $a"
        );

cmpthese(-5,
         {
             single => sub {
                 for my $s (@x)
                 {
                     my $x = $s;
                     $x =~ s/^\s+|\s+$//g;
                 }
             },
             double => sub {
                 for my $s (@x)
                 {
                     my $x = $s;
                     $x =~ s/^\s+//;
                     $x =~ s/\s+$//;
                 }
             },
             trick => sub {
                 for my $s (@x)
                 {
                     my $x = $s;
                     s/^\s+//, s/\s+$// for $x;
                 }
             },
             capture => sub {
                 for my $s (@x)
                 {
                     my $x = $s;
                     $x =~ s/\A\s*(.*?)\s*\z/$1/
                 }
             },
             kramercap => sub {
                 for my $s (@x)
                 {
                     my $x = $s;
                     ($x) = $x =~ /^\s*(.*?)\s*$/
                 }
             },
         }
        );