use strict;
use warnings;
use Benchmark qw(:all);

my $str = 'a' x 100;

my @matchwords = qw(
aol aachen aaliyah aaron abbas abbasid abbott abby abdul abe abel abelard abelson
aberdeen abernathy abidjan abigail abilene abner abraham abram abrams absalom abuja
abyssinia abyssinian ac acadia acapulco accra acevedo achaean
);

my $q1s = join('|', map { "$_\\s*\\w+" } @matchwords );
my $q1  = qr/$q1s/;

my @q2s = map { "$_\\s*\\w+" } @matchwords;
my @q2  = map { qr/$_/ } @q2s;

my $q3s = join('|', map { "($_)\\s*\\w+" } @matchwords );
my $q3  = qr/$q3s/;

my @q4s = map { "($_)\\s*\\w+" } @matchwords;
my @q4  = map { qr/$_/ } @q4s;

timethese( 100000, {
	'alternation, no grouping' => sub {
		$str =~ /$q1/;
	},
	'loop, no grouping' => sub {
		for my $qr ( @q2 ) {
			$str =~ /$qr/;
		}
	},
	'alternation, grouping' => sub {
		$str =~ /$q3/;
	},
	'loop, grouping' => sub {
		for my $qr ( @q4 ) {
			$str =~ /$qr/;
		}
	},
});

##</code><code>##

Benchmark: timing 100000 iterations ...
alternation, grouping: 12 wallclock secs (11.92 usr +  0.00 sys = 11.92 CPU) @ 8389.26/s (n=100000)
alternation, no grouping:  0 wallclock secs ( 0.19 usr +  0.00 sys =  0.19 CPU) @ 526315.79/s (n=100000)
            (warning: too few iterations for a reliable count)
loop, grouping:  2 wallclock secs ( 1.33 usr +  0.00 sys =  1.33 CPU) @ 75187.97/s (n=100000)
loop, no grouping:  1 wallclock secs ( 1.33 usr +  0.00 sys =  1.33 CPU) @ 75187.97/s (n=100000)