# perl 5.10.0:
timethis 10:  0 wallclock secs ( 0.33 usr +  0.00 sys =  0.33 CPU) @ 30.30/s (n=10)
            (warning: too few iterations for a reliable count)
# perl 5.8.8:
timethis 10: 79 wallclock secs (78.92 usr +  0.04 sys = 78.96 CPU) @  0.13/s (n=10)

##</code><code>##

use strict;
use warnings;

my @alphabet = ('a'..'z', 'A'..'Z', ' ');

sub random_string {
    my $length = int shift;
    return join '', map { @alphabet[int rand(@alphabet)] } 1..$length;
}

my $re = join '|', map { random_string(5+rand(10)) } 1..500;

my $target = random_string(1e2);

use Benchmark qw(timethis);

timethis(100_000, sub { $target =~ m/$re/ })