gistfile1.txt

use strict;
use warnings;

use Benchmark qw( cmpthese );

my $flag_off = 'A string of medium length containing < 100 characters';
my $flag_on  = 'A string of medium length containing < 100 characters';
utf8::upgrade($flag_on);

cmpthese(
    5_000_000,
    {
        'UTF-8 flag off' => \&off,
        'UTF-8 flag on'  => \&on,
    }
);

sub off {
    my $first = substr( $flag_off, 0,   10 );
    my $last  = substr( $flag_off, -10, 10 );
    $flag_off =~ /medium/;
    $flag_off =~ /(a|b|c|d|foo)/;
}

sub on {
    my $first = substr( $flag_on, 0,   10 );
    my $last  = substr( $flag_on, -10, 10 );
    $flag_on =~ /medium/;
    $flag_on =~ /(a|b|c|d|foo)/;
}