#!/net/perl/5.10.0/bin/perl
use strict;
use warnings;

use Benchmark qw(cmpthese);

my $str1 = join '', 'a' .. 'z';
my $str2 = join '', 'a' .. 'l', 'baz', 'm' .. 'z';
my $str3 = join '', 'a' .. 'z', 'a';

my $rx = qr/\Aabc(?!.*baz).*xyz\z/ms;

cmpthese(
    -1,
    {
        regex_match => sub { $str1 =~ /$rx/ },
        index_match => sub {
            substr( $str1, 0, 3 ) eq 'abc'
              && substr( $str1, -3 ) eq 'xyz'
              && index( $str1, 'baz' ) == -1;
        },
    }
);

cmpthese(
    -1,
    {
        regex_fail1 => sub { $str2 =~ /$rx/ },
        index_fail1 => sub {
            substr( $str2, 0, 3 ) eq 'abc'
              && substr( $str2, -3 ) eq 'xyz'
              && index( $str2, 'baz' ) == -1;
        },
    }
);

cmpthese(
    -1,
    {
        regex_fail2 => sub { $str3 =~ /$rx/ },
        index_fail2 => sub {
            substr( $str3, 0, 3 ) eq 'abc'
              && substr( $str3, -3 ) eq 'xyz'
              && index( $str3, 'baz' ) == -1;
        },
    }
);

__END__
                 Rate regex_match index_match
regex_match  337317/s          --        -73%
index_match 1228799/s        264%          --
                 Rate regex_fail1 index_fail1
regex_fail1  362337/s          --        -70%
index_fail1 1226609/s        239%          --
                 Rate regex_fail2 index_fail2
regex_fail2  865569/s          --        -48%
index_fail2 1653160/s         91%          --