gistfile1.txt

use strict;
use warnings;
use Benchmark qw(cmpthese);

my $slash = '/foo';
my $mid   = '?foo=bar&hoge=fuga';
my $long  = 'foo=bar&hoge=fuga'x100;

print "perl: $^V¥n";
print "OS  : $^O¥n";

bench($slash);
bench($mid);
bench($long);

sub bench {
    my $query = shift;
    print "### $query¥n";
    cmpthese(-1, {
        regex => sub {
            my $stuff = $query;
            $stuff =‾ s{^([^/])}{/$1};
        },
        index => sub {
            my $stuff = $query;
            unless (index($stuff, '/') == 0) {
                $stuff = "/$stuff";
            }
        },
        substr => sub {
            my $stuff = $query;
            unless (substr($query, 0, 1) eq '/') {
                $stuff = "/$stuff";
            }
        },
    }, 'all');
}

__END__
perl: v5.12.2OS  : darwin### /fooBenchmark: running index, regex, substr for at least 1 CPU seconds...     index:  0 wallclock secs ( 1.07 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.08 CPU) @ 2998378.70/s (n=3238249)
     regex:  1 wallclock secs ( 1.07 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.08 CPU) @ 1960477.78/s (n=2117316)
    substr:  0 wallclock secs ( 1.02 usr  0.00 sys +  0.00 cusr  0.00 csys =  1.02 CPU) @ 2570039.22/s (n=2621440)
            Rate  regex substr  index
regex  1960478/s     --   -24%   -35%
substr 2570039/s    31%     --   -14%
index  2998379/s    53%    17%     --
### ?foo=bar&hoge=fuga
Benchmark: running index, regex, substr for at least 1 CPU seconds...
     index:  0 wallclock secs ( 0.99 usr  0.03 sys +  0.00 cusr  0.00 csys =  1.02 CPU) @ 1226608.82/s (n=1251141)
     regex:  2 wallclock secs ( 1.13 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.14 CPU) @ 215578.07/s (n=245759)
    substr:  0 wallclock secs ( 1.08 usr  0.00 sys +  0.00 cusr  0.00 csys =  1.08 CPU) @ 1158463.89/s (n=1251141)
            Rate  regex substr  index
regex   215578/s     --   -81%   -82%
substr 1158464/s   437%     --    -6%
index  1226609/s   469%     6%     --
### foo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fugafoo=bar&hoge=fuga
Benchmark: running index, regex, substr for at least 1 CPU seconds...
     index:  1 wallclock secs ( 1.03 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.04 CPU) @ 300754.81/s (n=312785)
     regex:  1 wallclock secs ( 1.05 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.06 CPU) @ 190933.96/s (n=202390)
    substr:  1 wallclock secs ( 1.09 usr  0.01 sys +  0.00 cusr  0.00 csys =  1.10 CPU) @ 901120.00/s (n=991232)
           Rate  regex  index substr
regex  190934/s     --   -37%   -79%
index  300755/s    58%     --   -67%
substr 901120/s   372%   200%     --