use strict;
use warnings;
use feature 'say';
use re 'debug';

my $str = 'foobar';

sub foo { map /$str/, 1 .. 3 }

foo for 1 .. 2;

##</code><code>##

Compiling REx "foobar"
Final program:
   1: EXACT <foobar> (4)
   4: END (0)
anchored "foobar" at 0 (checking anchored isall) minlen 6
Compiling REx "foobar"
Compiling REx "foobar"
Compiling REx "foobar"
Compiling REx "foobar"
Compiling REx "foobar"

##</code><code>##

use strict;
use warnings;
use Benchmark qw( cmpthese timethese );

open my $words, "<", "linuxwords.txt" or die "$!";
my @words = <$words>;
chomp @words;

my @search = @words[0..10];

$" = "|";

my $re = qr/^(?:@words)$/;
my $str = "^(?:@words)\$";
my $str1 = $str;

my $r = timethese
(
    -5,
    {
        use_qr  => sub { map /$re/, @search },
        use_str => sub { 
            substr $str1, rand 400_000, 1, '#';     # 'equalize' conditions with 'use_str1'
            map /$str/, @search 
        },
        use_str1 => sub { 
            substr $str1, rand 400_000, 1, '#';     # force proper re-compilation below
            map /$str1/, @search 
        },
    }
);
cmpthese $r;

##</code><code>##

            Rate use_str1  use_str   use_qr
use_str1  3.65/s       --     -99%    -100%
use_str    436/s   11853%       --     -99%
use_qr   31592/s  865014%    7138%       --