use strict;
use warnings;

use Benchmark 'cmpthese';

my $sz      = ( shift || 10 ) - 4;
my $X = 'N' . 'x' x $sz . '000';
my $Y = 'N' . 'x' x $sz . '001';

print '# input length: ', length( $X ), $/;

cmpthese( -1,
          {
           '?!X'  => sub { scalar $X =~ /^N(?!.*00$).*$/ },
           '?!Y'  => sub { scalar $Y =~ /^N(?!.*00$).*$/ },
           '?<!X' => sub { scalar $X =~ /^N.*(?<!00$)$/  },
           '?<!Y' => sub { scalar $Y =~ /^N.*(?<!00$)$/  },
           }
        );