#!/usr/bin/perl

use strict;
use utf8;
use Benchmark ':all';

# the pattern doesn't even need to contain anything fancy
# for the problem to manifest itself
my $pattern = 'dumbest pattern ever';

# it's all about whether or not the /i flag is embedded into the regex
my $re   = qr/$pattern/;
my $re_i = qr/$pattern/i;

# qr//i causes a noticeable slowdown even when dealing with 7-bit (US-ASCII)
# strings, but this being multibyte seems to make things _a lot_ worse
my $str = 'очень длинная строка ' x 10;


my $count = 300_000;

cmpthese($count, {
    'qr//i+m//' => sub { $str =~ /$re_i/ },
    'qr//+m//i' => sub { $str =~ /$re/i },
    'qr//+m//'  => sub { $str =~ /$re/ }
});

##</code><code>##

$ ./qr-utf8.pl
              Rate qr//i+m// qr//+m//i  qr//+m//
qr//i+m//  10881/s        --      -98%      -98%
qr//+m//i 505263/s     4543%        --       -7%
qr//+m//  540845/s     4870%        7%        --