@strings = ( 'There was a bright man from Nantucket'
	    ,'Abba babbles about bubble blowers'
	    ,'Enough with the excess bs already'
	    ,'None at all in this one');
my @c;

use Benchmark 'cmpthese';

%methods = (
  'anch'  => sub { s/b(?=[^b]*$)/x/ for @c=@strings},
  'xeger' => sub { $_ = reverse, s/b/x/, $_ = reverse for @c=@strings },
  'plain' => sub { s/(.*)b/$1x/ for @c=@strings},
  '2part' => sub { /.*(?=b)/g and s/\Gb/x/ for @c=@strings },
  '2part-A' => sub { /b(?=[^b]*$)/g and s/\Gb/x/ for @c=@strings },
  'substr' => sub { substr($_, rindex($_, 'b'), 1) = 'x' for @c=@strings},
  'neglook' => sub { s/b(?!.*b)/x/ for @c=@strings }
);

cmpthese(-3, \%methods );