use strict;
use warnings;
my $s = do { local ( @ARGV, $/ ) = 'x'; <> };
$s =~ /x/;

##</code><code>##

$ /usr/bin/time -f %M perl fmap.pl

##</code><code>##

use strict;
use warnings;
use File::Map qw/ map_file /;
map_file my $s, 'x', '<';
$s =~ /x/;

##</code><code>##

$s =~ /x/; 
$s =~ /x/; 
$s =~ /x/; 
$s =~ /x/; 
$s =~ /x/;