Hi, the strange thing is that, replicating your benchmark (together with a third solution), I get a much higher advantage for the 'a' solution than what you got: 
$ perl -e 'use Benchmark(cmpthese);
cmpthese(1000000, {
     "a" => sub {
        $_ = "this that this those this these.";
        $a = () = /this/g;
    },
     "b" => sub {
        $_ = "this that this those this these.";
        $a++ while(s/this//);
    },
     "c"  => sub {
         $_ = "this that this those this these.";
         $a = s/this/this/g;
    }
});'
      Rate    a    b    c
a 282406/s   -- -28% -28%
b 390778/s  38%   --  -1%
c 393391/s  39%   1%   --

[download]
Note that I had to use one million iterations, with 100_000 I got the "too few iterations" warning.

In reply to Re^2: Count number of occurrence of word by Laurent_R
in thread Count number of occurrence of word by fattahsafa

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