#!/usr/bin/perl -w
use strict;
use Benchmark;

my ( $re, $test );

timethese(-30, {
    regex1  => '$re = "a" . \'\d\'x500 . "a";
                $test = ("a"x2000 . "1"x499)x2 . "a" . "1"x500 . ("a"x2000 . "1"x499)x2 ;
                $test =~ /$re/o;',
    regex2  => '$re = "a" . \'\d{500}\' . "a";
                $test = ("a"x2000 . "1"x499)x2 . "a" . "1"x500 . ("a"x2000 . "1"x499)x2 ;
                $test =~ /$re/o;',
});

##</code><code>##

Benchmark: running regex1, regex2, each for at least 30 CPU seconds...
    regex1: 31 wallclock secs (31.31 usr +  0.00 sys = 31.31 CPU) @ 655.10/s (n=20508)
    regex2: 31 wallclock secs (30.84 usr +  0.00 sys = 30.84 CPU) @ 530.35/s (n=16358)