try find the fastest way to convert a group string into index?

[learnfirst1]

On Sunday, 16 September 2018 at 11:51:24 UTC, learnfirst1 wrote:
> On Sunday, 16 September 2018 at 11:30:11 UTC, learnfirst1 wrote:
>> On Sunday, 16 September 2018 at 10:14:24 UTC, Vladimir 
>> Panteleev wrote:


I will test pcre solution vs mpfc for benchmark.  the pcre is 
easy to deal with low/up case.

The PCRE:

/^(?:Accept(*:0)|Accept\-Charset(*:1)|Accept\-Encoding(*:2)|Accept\-Language(*:3)|Access\-Control\-Allow\-Credentials(*:4)|Access\-Control\-Allow\-Origin(*:5)|Access\-Control\-Allow\-Methods(*:6)|Access\-Control\-Allow\-Headers(*:7)|Access\-Control\-Max\-Age(*:8)|Access\-Control\-Expose\-Headers(*:9)|Access\-Control\-Request\-Method(*:10)|Access\-Control\-Request\-Headers(*:11)|Age(*:12)|Allow(*:13)|Authorization(*:14)|Cache\-Control(*:15)|Connection(*:16)|Content\-Encoding(*:17)|Content\-Language(*:18)|Content\-Length(*:19)|Content\-Location(*:20)|Content\-Range(*:21)|Content\-Security\-Policy(*:22)|Content\-Type(*:23)|Cookie(*:24)|Date(*:25)|ETag(*:26)|Expect(*:27)|Expires(*:28)|Host(*:29)|If\-Match(*:30)|If\-Modified\-Since(*:31)|If\-None\-Match(*:32)|If\-Range(*:33)|If\-Unmodified\-Since(*:34)|Last\-Modified(*:35)|Location(*:36)|Origin(*:37)|Pragma(*:38)|Proxy\-Authenticate(*:39)|Proxy\-Authorization(*:40)|Range(*:41)|Referer(*:42)|Retry\-After(*:43)|Sec\-Websocket\-Extensions(*:44)|Sec\-Websocket\-Key(*:45)|Sec\-Websocket\-Origin(*:46)|Sec\-Websocket\-Protocol(*:47)|Sec\-Websocket\-Version(*:48)|Server(*:49)|Set\-Cookie(*:50)|Strict\-Transport\-Security(*:51)|Transfer\-Encoding(*:52)|Upgrade(*:53)|User\-Agent(*:54)|Vary(*:55)|Via(*:56)|WWW\-Authenticate(*:57))$/i