use strict; 
use Benchmark 'cmpthese';

foreach my $regexcount (10) 
{ 
    foreach my $regexlength (5,20) { 
        my @items    = map{ createRandomTextWithLength($regexlength) } (1..$regexcount); 
        my $regexstr = join('|',@items); 
        my $regex    = qr/(?:$regexstr)/; 

        foreach my $stringlength (1000,100000) { 
            print join "\n", "Stringlength: $stringlength",
                "Number of Regexes:$regexcount", "Length of each Regex:$regexlength\n"; 
            my $teststring = createRandomTextWithLength($stringlength);
            cmpthese(-2, {
                alt => sub {
                    my $test=$teststring; 
                    $test =~ s/$regex/foobar/g; 
                },
                for => sub {
                    my $test=$teststring;
                    foreach my $oneregex (@items) {
                        $test =~ s/$oneregex/foobar/g;
                    }
                }
            });
        } 
    }
} 

sub createRandomTextWithLength($) 
{ 
    my($count) = (@_); 
    my $string; 
    for (1.. $count) { $string.=chr(ord('a')+rand(20)) } 
    return $string; 
}