#!/usr/bin/env perl
use Benchmark 'cmpthese';

my %ways =
  (
   '3calls' => sub {/a/ && !/b/ && /c/},
   code     => sub {m:^(?(?{/a/ && !/b/ && /c/})|(?!)):},
   pos_look => sub {/(?=.*a)(?!.*b)(?=.*c)/s},
   neg_look => sub {/(?!(?!.*a)|(?=.*b)|(?!.*c))/s},
   neg_anch => sub {/^(?!(?!.*a)|(?=.*b)|(?!.*c))/s}
  );

# Minimal check that the regexps do what they're supposed to
while (my ($way, $sub)=each %ways) {
  die "$way failed to match\n" unless ($_ = 'cat') && &$sub;
  die "$way had a false positive\n" if ($_= 'cab') && &$sub;
}

print "For matching:\n";
$_="find your cat";
cmpthese(-1, \%ways);

print "For non-matching:\n";
$_="don't find a cab";
cmpthese(-1, \%ways);
__END__
              Rate  code neg_look neg_anch pos_anch pos_look   3calls
code      674093/s    --     -52%     -53%     -63%     -63%     -87%
neg_look 1417081/s  110%       --      -1%     -21%     -22%     -73%
neg_anch 1429846/s  112%       1%       --     -21%     -21%     -73%
pos_anch 1798791/s  167%      27%      26%       --      -1%     -66%
pos_look 1810887/s  169%      28%      27%       1%       --     -66%
3calls   5338256/s  692%     277%     273%     197%     195%       --
For non-matching:   
              Rate  code neg_anch neg_look pos_anch pos_look   3calls
code      674093/s    --     -55%     -57%     -63%     -65%     -88%
neg_anch 1495898/s  122%       --      -5%     -17%     -22%     -73%
neg_look 1570933/s  133%       5%       --     -13%     -18%     -72%
pos_anch 1806441/s  168%      21%      15%       --      -5%     -67%
pos_look 1906963/s  183%      27%      21%       6%       --     -65%
3calls   5522908/s  719%     269%     252%     206%     190%       --