text:
A Different Kind of Meta Regex Golf

Notice: Following popular demand I have slightly relaxed the rules:

The maximum regex size grows by 1 byte every 5 answers. Answer N may use up to 29 + ⌈N/5⌉ bytes.
The score of each answer will be (M/(30+N/5))N

In regex golf, you're given two sets of strings, and are asked to create the shortest regex which matches all strings in the first set, but fails on all strings in the second set.
That is what we're going to do, but each time someone answers, their regex itself will be added to one of the two sets of strings (of their own choice). Therefore, there is a strict order to answers in this challenge.
Let's go through an example:

Say I start this with abc (which I won't), and put it in the match set.
Then a valid second answer would be a, as it matches the above (and there are no strings that need to fail yet). Say this answer goes in the fail set.
Now the third answer has to match abc but fail on a. A possible third answer is therefore b. Let's put this in the match set.
The fourth answer now has to match abc and b, but fail on a. We'll disallow duplicate answers, so a valid regex would be c|b.

What's important is that your answer should be as short as possible. This may be trivial for the first few answers, but once we get a few answers, it should get harder and harder to get the desired match in as few characters as possible.
For the actual challenge, initially the match set contains PPCG and the fail set contains [PPCG], and I have already provided the first answer.
Answering
The key thing to understand about this challenge is that only one person can answer at a time and each answer depends on the one before it.
There should never be two answers with the same N. If two people happen to simultaneously answer for some N, the one who answered later (even if it's a few seconds difference) should graciously delete their answer.
To make this run a bit smoother, try to stick to the following steps when posting your answer:

Make sure that someone has independently verified the correctness of the previous answer (and left a corresponding comment).
Take the two test sets found in the previous answer, and write a regex which matches all strings in one set and none in the other.
Post your answer in the following format:
# N. [regex flavour] - [regex size in bytes]

    [regex]

[link to online regex tester]

[notes, explanation, observations, whatever]

### The next answer has to match the following strings:

    [match set]

### And fail on these strings:

    [fail set]

where N is the number of your answer. Please copy [match set] and [fail set] from the previous answer, and append your regex to one of them.
This is absolutely vital to the challenge! I've provided a dashboard tool for the challenge to help with the bookkeeping, and it relies on the above template. (See bottom of the post.)
Another user should now review your submission and leave a comment "Correctness verified" if your answer follows all the rules (see below). If it doesn't, they should leave a comment pointing out any flaws. You've then got 15 minutes to fix those issues. If you don't, your answer will be deemed invalid, should be deleted, and someone else may post a follow-up answer to the previous one. (If this happens, you're free to submit a new answer any time.)

These regulations may seem rather strict, but they are necessary to avoid invalid answers somewhere up the chain.
Rules

A user may only submit one answer per 4 hour period. (This is to prevent users from constantly watching the question and answering as much as possible.)
A user may not submit two answers in a row. (e.g. since I submitted answer 1 I can't do answer 2, but I could do 3.)
Do not edit answers that have been verified. (Even if you find a way to shorten it!)
Should a mistake be discovered earlier in the chain (i.e. after follow-up answers have been posted), the offending answer should be deleted and will be removed from the set of strings that new submissions should fail on. However, all answers that have been posted since should not be changed to reflect.
Clearly state one flavour your regex is valid in. You may choose any flavour that is freely testable online. There's a good list of online testers over on StackOverflow. In particular, Regex101 and RegexPlanet should be useful, as they support a wide variety of flavours. Please include a link to the tester you chose in your answer. By switching on the global and multiline modifiers in the tester, you can test all strings at once, one on each line (these modifiers are not counted towards your regex size, because they aren't needed on any individual string).
Your regex must not be empty.
Your regex for answer N must not be longer than 29 + ⌈N/5⌉ bytes. I.e. answers 1 to 5 may use up to 30 bytes (inclusive), answers 6 to 10 may use up to 31 bytes... answers 31 to 35 may use up to 36 bytes. Check the dashboard to see how many characters the next answer may use.
Your regex must not be identical to any string in either test set.
Do not include delimiters in your submission or byte count, even if the relevant host language uses them. If your regex uses modifiers, add one byte per modifier to the regex size. E.g. /foo/i would be 4 bytes.

Scoring
Each answer's score is calculated as (M/(30+N/5))N, where M is the size of the regex in bytes, and N is it's number. Each user's score is the product of all their answers. The user with the lowest overall score wins. In the unlikely event of a tie, the user with the latest submission wins. I will accept that user's latest answer.
If you prefer summing scores, you can calculate each answer's score as N * (log(M) - log(30)) and sum those up over all answers. That will give the same leaderboard order.
There is no need to include an answer's score in the answer, just report M. The challenge dashboard at the bottom of the question will compute the scores, and in the event of two very close scores, I'll double check the results using arbitrary-precision types.
Note that the score of each answer is less than 1, so you can improve your overall score by providing a new answer. However, the shorter each of your submissions, the more efficiently you can lower your score. Furthermore, later answers can achieve a lower score although being longer, due to the increasing exponent.
Dashboard
I've written a little Dashboard tool, using Stack Snippets, based on Optimizer's work over here. I hope this will help us get some order into these answer-dependent challenges.
This will display the current status of the challenge - in particular, if there are conflicting answers, if an answer needs to be verified, or if the next answer can be posted.
It also produces a list of all answers with scores, as well as a leaderboard of all users. Please stick to the challenge format above, so the dashboard can read out the relevant strings from your answers. Otherwise you might not be included in the leaderboard.
Please let me know (ideally in chat) if you spot any bugs or have some ideas how the usefulness of the tool could be improved.

function answersUrl(e){return"http://api.stackexchange.com/2.2/questions/"+QUESTION_ID+"/answers?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+ANSWER_FILTER}function commentsUrl(e,t){return"http://api.stackexchange.com/2.2/answers/"+e+"/comments?page="+t+"&pagesize=100&order=asc&sort=creation&site=codegolf&filter="+COMMENT_FILTER}function getAnswers(){$.ajax({url:answersUrl(page++),method:"get",dataType:"jsonp",crossDomain:true,success:function(e){answers.push.apply(answers,e.items);if(e.has_more)getAnswers();else{page=1;getFinalComments()}}})}function getFinalComments(){answers=answers.filter(shouldHaveHeading);answers=answers.filter(shouldHaveScore);$.ajax({url:commentsUrl(answers[0].answer_id,page++),method:"get",dataType:"jsonp",crossDomain:true,success:function(e){comments.push.apply(comments,e.items);if(e.has_more)getAnswers();else process()}})}function shouldHaveHeading(e){var t=false;try{t|=/^(#|<h).*/.test(e.body_markdown);t|=["-","="].indexOf(e.body_markdown.split("\n")[1][0])>-1}catch(n){}return t}function shouldHaveScore(e){var t=false;try{t|=SIZE_REG.test(e.body_markdown.split("\n")[0])}catch(n){}return t}function findDuplicates(e){var t=false;var n={};e.forEach(function(e){var r=e.body_markdown.split("\n")[0].match(NUMBER_REG)[0];if(n[r])t=t||r;n[r]=true});return t}function hasBeenVerified(e,t){var n=false;t.forEach(function(t){n|=/correctness verified/i.test(t.body_markdown)&&e!=t.owner.user_id});return n}function userTimedOut(e){return NOW-e.creation_date*1e3<MSEC_PER_ANSWER}function getAuthorName(e){return e.owner.display_name}function getAnswerScore(e,t){e=parseInt(e);t=parseInt(t);return Math.pow(t/(30+e/5),e)}function process(){$("#last-user").append(answers[0].owner.display_name);var e=answers.slice(1).filter(userTimedOut).map(getAuthorName).join(", ");if(e)$("#timed-out-users").append(e);else $("#timed-out-notice").hide();var t=answers[0].body_markdown.split("\n")[0].match(NUMBER_REG)[0];var n=findDuplicates(answers);if(n){var r=$("#status-conflict-template").html();$("#challenge-status").append(r.replace("{{NUMBER}}",n));$("#challenge-status").addClass("conflict")}else if(!hasBeenVerified(answers[0].owner.user_id,comments)){var r=$("#status-verification-template").html();$("#challenge-status").append(r.replace("{{NUMBER}}",t));$("#challenge-status").addClass("verification")}else{var r=$("#status-next-template").html();$("#challenge-status").append(r.replace("{{NUMBER}}",t).replace("{{NEXT}}",parseInt(t)+1).replace("{{SIZE}}",29+Math.ceil((parseInt(t)+1)/5)));$("#challenge-status").addClass("next")}var i={};var s={};answers.forEach(function(e){var t=e.body_markdown.split("\n")[0];var n=$("#answer-template").html();var r=t.match(NUMBER_REG)[0];var o=(t.match(SIZE_REG)||[0])[0];var u=getAnswerScore(r,o);var a=getAuthorName(e);n=n.replace("{{NAME}}",a).replace("{{NUMBER}}",r).replace("{{SIZE}}",o).replace("{{SCORE}}",u.toExponential(5)).replace("{{LINK}}",e.share_link);n=$(n);$("#answers").append(n);i[a]=(i[a]||1)*u;s[a]=(s[a]||0)+1});var o=[];for(var u in i)if(i.hasOwnProperty(u)){o.push({name:u,numAnswers:s[u],score:i[u]})}o.sort(function(e,t){return e.score-t.score});var a=1;o.forEach(function(e){var t=$("#user-template").html();t=t.replace("{{NAME}}",e.name).replace("{{NUMBER}}",a++).replace("{{COUNT}}",e.numAnswers).replace("{{SCORE}}",e.score.toExponential(5));t=$(t);$("#users").append(t)})}var QUESTION_ID=41462;var ANSWER_FILTER="!*cCFgu5yS6BFQP8Z)xIZ.qGoikO4jB.Ahv_g-";var COMMENT_FILTER="!)Q2B_A497Z2O1kEH(Of5MUPK";var HOURS_PER_ANSWER=4;var MSEC_PER_ANSWER=HOURS_PER_ANSWER*60*60*1e3;var NOW=Date.now();var answers=[],comments=[],page=1;getAnswers();var SIZE_REG=/\d+(?=[^\d&]*(?:<(?:s>[^&]*<\/s>|[^&]+>)[^\d&]*)*$)/;var NUMBER_REG=/\d+/
body{text-align:left!important}#challenge-status{font-weight:700;padding:10px;width:620px}#blocked-users{padding:10px;width:620px}.conflict{background:#994343;color:#fff}.verification{background:#FFDB12}.next{background:#75FF6E}#last-user,#timed-out-users{font-weight:700}#answer-list{padding:10px;width:300px;float:left}#leaderboard{padding:10px;width:290px;float:left}table thead{font-weight:700}table td{padding:5px}
 <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b">

 User  has posted the last answer, and may not post the next one.
 have answered within the last four hours and may not answer again yet. (If a user appears in this list twice, they must have answered twice within four hours!)

List of Answers (newest first)

No.	Author	Size	Score

Leaderboard

No.	User	Answers	Score

{{NUMBER}}	{{NAME}}	{{SIZE}}	{{SCORE}}	Link

{{NUMBER}}	{{NAME}}	{{COUNT}}	{{SCORE}}

 There is more than one answer with number {{NUMBER}}!
Please resolve this conflict before posting any further answer.

 Answer {{NUMBER}} has not been verified!
Please review the answer and post a comment reading "Correctness verified." on the answer if it is valid. Note that this has to be done by a different user than the author of the answer!

 Answer {{NUMBER}} has been verified!
You may now post answer {{NEXT}}, using up to {{SIZE}} bytes.

The rules turned out to be a bit stricter than I intended. After some discussion in chat I'm considering to relax the rules a little after the bounty has run out. I'll post 3 comments for the options I can think of below. Please indicate your preference by voting on the comments.

Rules are rules. Don't change them. It might be a shame that it's pretty much impossible to post another answer, but that doesn't justify changing the rules.

Allow for an additional byte every 10 answers. Correspondingly, change the answer score to (M/(30+N/10))^N. This would be applied retroactively, so the next answer could use up to 32 bytes. The change in scoring would not affect the top two places on the leaderboard, but the other users would be shuffled somewhat.

Allow for an additional byte every 5 answers. Correspondingly, change the answer score to (M/(30+N/5))^N. This would be applied retroactively, so the next answer could use up to 35 bytes. The change in scoring would not affect the top two places on the leaderboard, but the other users would be shuffled somewhat.

(Note that the order of the leaderboard changes, because the alternative scoring methods would give a bigger advantage to late answers, with the 5-answer option emphasising late answers even more than the 10-answer option. This is probably a good thing, because I've received several complaints that the easy, early answers had too much of an advantage over late answers in the original rules.)

You people are strange and twisted. Why would you do this to yourselves? (It's fun to read though :P)

42. Python flavour - 38
\?[^w$]*\$$|^P|\w.\)|w.?\+|w\^|[^?P]P$

Tested on Regex101
The lack of entropy in the last few answers was getting to me... (should have done this sooner)
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)
\w.\)|\?[^-$]*\$$|[]^C]\w$|w[+^]
[]^C]\w$|\w.\)|-\$|w[+^]|\?[^w$]*\$$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$
[]^C]\w$|\w.\)|w[[+^]|\?[^w$]*\$$
\?[^w$]*\$$|^P|\w.\)|w.?\+|w\^|[^?P]P$

Correctness verified.

My program struggles to find an answer less than 45 characters long...

@Vi. Well I can say that a 38 solution does exist at least, but of course it'd be interesting if someone manages to get lower :)

28. Python flavour - 29
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P

Tested on Regex101
Lots of fiddling around was done - #4 in the pass set's probably the biggest pain, as it's a substring of a regex in the fail set, and also shares a suffix with another regex in the fail set.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\

Correctness verified.

24 - Python flavour - 29
^(..[^^].{4,22}\$|[^?]+\w)$|2

Tested here
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2

Correctness verified.

8. ECMAScript flavour - 14 bytes
[^?][PG]$|<|PG

Demo
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG

Correctness verified.

Fixed the demo link.

@FryAmTheEggman The script does read the comments, but only looks for "correctness verified" as a substring (ignoring case).

@MartinBüttner Thanks, good to know.

+1 for singlehandedly making this challenge 10 times harder

10. Python flavor - 19
^[\w^]*$|!|]P|G]\$$

Tested on Regex101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)*[^\\|]*[^\]]$

Correctness verified.

2. ECMAScript flavour - 6 bytes
^[P\^]

Test it here
The next answer has to match the following strings:
PPCG
^P

And fail on these strings:
[PPCG]
^[P\^]

Correctness verified.

9. Python flavour - 28
^[^\\|]*(\\\\)*[^\\|]*[^\]]$

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)*[^\\|]*[^\]]$

I also found this not to work a minute ago. It requires two backslashes in a row to match so I don't think a flag could save it.

Whoops.... Should have been a * instead of +. I edited my answer

Correctness verfied.

11. Python - 29
^(.{,4}|.{9}|.{16,19}|.{5}P)$

► Test at RegexPlanet
Almost all invalid answers have a different length than all the valid ones. This regex makes use of that.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$

Correctness verified.

23. PCRE flavour - 28
([^\\}<]{3}|][^]]|^).?[$PG]$

Tested on Regex101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$

What does [^] do?

@feersum In most flavours, a ] as the first element of a character class (after optional negation), is just a ] inside the character class and doesn't close (because empty character classes are a bit pointless). So [^]] matches anything but ]. The notable exception is ECMAScript, which does allow empty character classes. In that case [] doesn't match anything, it acts like (?!) and [^] matches any character, which is convenient, because ECMAScript doesn't have an s modifier, and [\s\S] is a pain to type an read.

Correctness verified.

29. PCRE flavour - 28
^..(.[!)3G^w]|$)|\^.{7}$|G\)

Tested on Regex101
This answer still works...
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\

Correctness verified.

Nice! Barring reshuffling, that's exactly what I had

I was trying to calculate this using genetic algorithm, but it produced only 30-character regex... Now running it to get the next answer. Current result - 32 characters.

@Vi A genetic algorithm eh, interesting ideas you have there :P

@Sp3000, Now 30 characters... But another anwser has arrived, so need to restart.

31. Perl flavour - 29
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
I don't know how it works, it was produced by my the first foray into genetic algoritms. There is program output that mentions the answer.
The next answer has to match:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

and to fail:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$

Correctness verified.

Ahaha nice - did you use the previous answers as seeds for the population or did it just end up looking like the previous one?

The passing and failing strings are used as initial building blocks. They hovewer got banned after some time due to being local minimums. You can see how it goes in the program log: the number in parentheses after "metric=" is the measure of how fast we are going forward. It it's low for long, we ban current answers and reset.

(Meanwhile, 31-character candidate for next answer is already found)

Oh, the limit increased? It's not 29? This way it is not going to end soon... I though the main challenge is to find the last, the ultimate regex.

If it stayed at 29, your regex would probably have been last ;) (I do have a 30 though)

My program have also already printed the 30-character one. Let's consider "The last not-more-than-29 answer" a side challenge.

32. PCRE — 30 bytes
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)

Correctness verified.

Why is it added to "fail" list? It already fails on itself, so can serve as the next answer without modifications. I suppose for each answer there is no choice of to which list it is to be appended.

@Vi. I guess hwnd's feeling nice today

I'll make it harder as it keeps going.

1. ECMAScript flavour - 2 bytes
^P

Test it on Regex101.
The initial matching set is PPCG and the failing set [PPCG]. Therefore, this regex simply tests that the string starts with P.
The next answer has to match the following strings:
PPCG
^P

And fail on these strings:
[PPCG]

Correctness verified.

3. ECMAScript flavour - 6 bytes
[^\]]$

Test it here
The next answer has to match the following strings:
PPCG
^P

And fail on the these strings:
[PPCG]
^[P\^]
[^\]]$

Correctness verified.

7. Python flavour - 16
(?<!\\..)(?!]).$

Tested on Regex101
Gotta add a \ to the match list :)
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P

Correctness verified.

This…this is devious.

@WChargin Thanks :) You should check out some of user23013 or n̴̖̋h̷͉̃a̷̭̿h̸̡̅ẗ̵̨́d̷̰̀ĥ̷̳ answers; some are quite 'devious' ;)

12. ECMAScript flavor - 17
!|[^?]P(CG|G..)?$

Test it here.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$

Correctness verified.

22. PCRE Flavor – 29 bytes
Since the original #22 is not modified for 1 hour I assume it has become invalid.
^.{3,23}[.-~]..\$$|[^P?][PG]$

Demo
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P

Correctness verified. (And yes, that's right, the previous 22 is now invalid.)

26. Python flavor - 28
^..(.[!G)(3w^]|.{7}$|$)|\$\?

Test on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~

Correctness verified.

30. Python flavour - 28
[[?C(].[-!)|w]|^P|^[^C|\\]*$

Tested on Regex101
When there's a will...
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$

Correctness verified.

37. Perl flavour - 30
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)

Submission on Regex101.
The solution was produced by the the same program as before. The program has also printed 29-character solution \?[^$w]*\$|[]^C]\w)$|w.]|\w.\, I don't know why, as it looks like a malformed regex...
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)

Correctness verified.

Ahaha I'm pretty annoyed I didn't get this after coming so far with the first half :P

40. PCRE — 33 bytes
[]^C]\w$|\w.\)|w[[+^]|\?[^w$]*\$$

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)
\w.\)|\?[^-$]*\$$|[]^C]\w$|w[+^]

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$
[]^C]\w$|\w.\)|w[[+^]|\?[^w$]*\$$

Correctness verified.

I have a 35 but I'm not satisfied with it so I'm going to see if I can get something more interesting

And I have 3 options for a 32-character answer, but the whole challenge got a bit boring (especially bookkeeping of Regex101 submissions and lists of fail/pass strings). If somebody wants, I can post an answer.

4. ECMAScript flavour - 5 bytes
^\^?P

Test it here.
The next answer has to match the following strings:
PPCG
^P

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P

Correctness verified.

5. ECMAScript flavour - 6 bytes
^[P^]P

Tested on Regex101.
Time to spice things up a bit with the success set.
The next answer has to match the following strings:
PPCG
^P
^[P^]P

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P

Correctness verified.

6. ECMAScript flavour - 9 bytes
[^?][PG]$

Tested on Regex101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P

Correctness verified.

14. PCRE flavour - 25
([.$?]|G\])\$$|^\^?P|\]P$

Tested on Regex101
This is starting to get quite hard.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$

Correctness verified.

15. PCRE flavour - 26
([P.$?]\$|[]^]P|G\]\$|CG)$

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$

Correctness verified.

16. PCRE flavor - 21
^[^?]*[PG]$|[?$].*\$$

Tested on Regex 101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$

It doesn't match PPCG.

@user23013 fixed

Correctness verified.

25. PCRE flavour - 29
^(..[^^].{4,22}\$|[^?]+\w)$|~

Tested here. (The test regex contains an additional \n to make sure that no match spans multiple lines. This is not necessary to match each individual string.)
That was a low-hanging fruit! :) I have to congratulate plannapus though, this regex is amazingly elegant for the current test sets. If you want to upvote this answer, make sure to upvote the previous one, too!
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~

Correctness verified.

35. PCRE — 35 bytes
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)

My verifier shows no errors.

Correctness verified. (@Vi., the dashboard looks for this specific phrase.)

I though about using that phrase, but was not sure if I want to make my comment authoritative.

My other 34-character answer mentioned before seems to work here. Waiting for 4 hours (or like that)...

I don't bother hacking up - I delegate it to the computer. Maybe write an answer-posting bot using StackExchange API?..

36. Python flavour - 32
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)

Tested on Regex101
I had three 32-byte regexes ready, and luckily one of them still works :D
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)

Correctness verified.

Correctness as a Perl regex is also verified.

Let's hope the question be inactive until tomorrow, as I have a pending 30-character answer to post.

38. Python flavour - 31
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$

Tested on Regex101
I'm feeling pretty silly now, because Vi. golfed out a useless + from my last answer.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$

Correctness verified.

My solver immediately found a 32-character solution - a variation on the same theme.

@Vi. I'm expecting this to continue until someone breaks \?[^w$]*\$$

So, nobody else want to post an answer?

Feel free, I'm observing.

39. Perl flavour - 32
\w.\)|\?[^-$]*\$$|[]^C]\w$|w[+^]

Regex101 submission
Generated by the program. There are also 2 competing 32-character solutions.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)
\w.\)|\?[^-$]*\$$|[]^C]\w$|w[+^]

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$

Correctness verified.

41. PCRE - 36
[]^C]\w$|\w.\)|-\$|w[+^]|\?[^w$]*\$$

Tested on Regex101
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)
\?[^w$]*\$$|[]^C]\w+$|w\^|\|..\)
\w.\)|\?[^-$]*\$$|[]^C]\w$|w[+^]
[]^C]\w$|\w.\)|-\$|w[+^]|\?[^w$]*\$$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]
^P|!.3|w\^|^[^C\\|]+$|\.[)$-](?!.!)
\?[^$w]*\$$|[]C^]\w$|w.]|\w.\)
\$..\\|\?[^w$]*\$$|w\^|[]^C]\w$
[]^C]\w$|\w.\)|w[[+^]|\?[^w$]*\$$

Correctness verified.

13. PCRE flavor - 20
[^])]\$|^\^?P|P.\].$

Test it here.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$

The previous answer (mine) has not been verified yet, so I hope it's valid so you don't lose your work.

@hsl taken care of that. user23013, please watch out for that next time ;)

Correctness verified.

17. Python flavor - 21
^[^[]P|]P|(G]|[.])\$$

Tested on Regex 101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$

Correctness verified.

18. PCRE Flavor - 25 bytes
!|((G.|P|\.)\$|[^?]P|CG)$

Tested on Regex 101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$

I got ninja'd :)

@FryAmTheEggman I'm sorry! Hopefully it isn't too different.

Actually mine still works, just going to verify yours :)

Oh good! I figured putting my new regex in the match would make it easier on future ones.

Correctness verified.

19. Python flavour - 28
\..$|!|\|G|^[\^P]P|P\^|G.\$$

Tested on Regex101.
I tried so many different ways. All 28 characters. :'(
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$

Correctness verified.

20. PCRE flavour - 27
...\^.P|^!|G]\$$|w|<!|^\^?P

Tested on Regex101.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P

Correctness verified.

21. ECMAScript flavour - 24 bytes
... The moment when you see one accept string is the prefix of a reject string, and realize that the longer one is from your earlier answer.
^[(!P]|G..$|]..\||[^?]P$

Demo
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P

Please also check the input/output if I messed up my copy/paste.

Correctness verified.

27. PCRE Flavor - 27
^..(.[!()3G^w]|.{7}$|$)|G\\

Demo. The previous answer clearly works, so... thanks? :)
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\

Correctness verified.

33. Python flavour - 30
^...[3w!G)]|^[^\\C|]*$|G.?.?\)

Tested on Regex101
Originally I had the 30 char [.!w].[]?3P]|^P|^[^C|\\]*$|\?< for the previous set, but I took too long trying to find a 29 and hwnd inadvertedly ruled out my submission.
So instead I mashed together two common themes we've had so far, just for fun :)
Note: Please remember that when testing ^[^C|\\]*$ or anything else that uses [^...], put a \n in the character set. Otherwise Regex101 may match over lines.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)

Correctness verified.

34. Perl flavour - 34
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]

Submission on Regex101 - there is additional \n added for Regex101 there, as previous answer suggested
The solution was produced by the the same program as before (with little tweaks). 35-character solutions were easy to find, but I waited for 34 version to make 34'th answer be 34 characters.
The next answer has to match the following strings:
PPCG
^P
^[P^]P
[^?][PG]$
(?<!\\..)(?!]).$
^[\w^]*$|!|]P|G]\$$
!|[^?]P(CG|G..)?$
[^])]\$|^\^?P|P.\].$
([.$?]|G\])\$$|^\^?P|\]P$
([P.$?]\$|[]^]P|G\]\$|CG)$
!|((G.|P|\.)\$|[^?]P|CG)$
^[(!P]|G..$|]..\||[^?]P$
^.{3,23}[.-~]..\$$|[^P?][PG]$
^..(.[!G)(3w^]|.{7}$|$)|\$\?
\.\)|P[.$?]|w\^|^[^|C\\]*$|^P
^..(.[!)3G^w]|$)|\^.{7}$|G\)

And fail on these strings:
[PPCG]
^[P\^]
[^\]]$
^\^?P
[^?][PG]$|<|PG
^[^\\|]*(\\\\)+[^\\|]*[^\]]$
^(.{,4}|.{9}|.{16,19}|.{5}P)$
^[^?]*[PG]$|[?$].*\$$
^[^[]P|]P|(G]|[.])\$$
\..$|!|\|G|^[\^P]P|P\^|G.\$$
...\^.P|^!|G]\$$|w|<!|^\^?P
([^\\}<]{3}|][^]]|^).?[$PG]$
^(..[^^].{4,22}\$|[^?]+\w)$|2
^(..[^^].{4,22}\$|[^?]+\w)$|~
^..(.[!()3G^w]|.{7}$|$)|G\\
[[?C(].[-!)|w]|^P|^[^C|\\]*$
[?[CP(].[-<)|w]|^P|^[^C|\\]*$
^..(.{7}$|.[3Gw!^)]|$)|G.?.?\)
^...[3w!G)]|^[^\\C|]*$|G.?.?\)
^[^C\\|]+$|G.\)|\.\)|w\^|^P|\...?]

There is also another 34 variant, substationally different with the posted one.

Correctness verified.

authors: n̴̖̋h̷͉̃a̷̭̿h̸̡̅ẗ̵̨́d̷̰̀ĥ̷̳

authors: خالد العتيبي


text:
Treasure Hunting on a Deserted Island
Introduction
You are stranded on a deserted island with some servants and are hunting for treasure. The longer one searches, the more treasure one finds. The fewer people searching, the more each person finds.
Due to limited supplies, the leader has decided that a few people, up to a quarter of the group, shall be left to die each night. He has decided not to tell anyone exactly how many people shall die on any given day ahead of time.
You are in control of a small group of 5 people, who shall venture out of camp to find treasure for you.
Objective
The objective of this competition is to amass as much treasure as possible. Every turn that your servants do not attempt to return to camp, they will find a certain number of pieces of treasure. Your servants may return to camp at different times.
Each turn that a worker stays out to search for treasure, the worker finds 1+R pieces of treasure, where R is the number of workers (out of all the bots) already back in camp. Dead bots do not factor into this calculation.
At the start of each day, a random number (n) from 2 to max(3, floor(num_live_players/4)) will be chosen. (For 10 players on day 1, this is 2 to max(3,50/4)=12. For 20 players on day 1, this would be 2 to max(3,100/4)=25.) This number represents the number of players who will be left to die for that day, and will not be given to your program.
If a servant is one of the last n people to return, he/she will die and be unable to transfer the treasure he/she found to your possession. Furthermore, the servant will be unable to participate in treasure hunting for the rest of the adventure.
Your final score is the average amount of treasure you obtained per adventure (run of the controller).
If more people attempt to return to camp on the same turn than there are open slots, random numbers will determine who gets in and who dies.
A day on this island from sunrise to sunset lasts 30 turns. As there are many dangerous animals at night, failure to return by sunset means that you will not be allowed into the camp.
Input/Output
Your program should run for the entirety of the simulation.
At the start of the simulation, INDEX I will be inputted, where I is the index of your bot (this index is counted from 1 up).
At the start of each day, START_DAY D/N will be inputted to your program, where D is the day number (starting from 1), and N is equal to max(3, floor(num_live_players/4)), which is the maximum number of people who may die on that particular day.
At the start of each turn, START_TURN T will be inputted to your program, where T is the turn number (starting from 1).
Once your program receives this, it should respond with a list of your servants' moves, each separated by a comma.
Valid moves are:

R: Try to return to camp.
S: Stay looking for treasure.
N: Servant is already dead or in camp.

Entering an invalid move will be interpretted as S if the bot is alive and not in camp, and N otherwise.
At the end of each turn, a string shall be passed to your program:
END_TURN [Turn #] [Bot 1 Moves] [Bot 2 Moves] ...

where each bot's servants' moves are separated by commas.
These moves will be one of the following:

R: Successfully returned to camp that turn.
r: Failed to return to camp that turn.
S: Still looking for treasure.
D: Died on an earlier turn.
N: Already back at camp.

Bots and servants remain in the same order throughout the entire simulation.
For example:
INDEX 2
....
END_TURN 8 N,N,N,N,N r,r,r,r,D D,D,D,N,R S,D,D,N,D

Here, you are the second bot (r,r,r,r,r), who tried to return all four servants that are still alive (and unluckily failed on all four). Bot 1's servants are all back in camp. Bot 3 has three dead servants, one more back in camp, and a fifth servant who successfully returned. Bot 4 has one servant who stayed (and will die, as this is the last turn of a day), one servant in camp, and three dead servants.
After each of these strings, unless a string signaling the end of the day has also been outputted (see below), your program is to output your servants' next moves, separated by commas. All servants must be accounted for (with N if already in camp, and D if already dead). Invalid moves will be treated as S if the servant is not already in camp/dead.
Example:
N,N,S,S,R

which means:
Servant # | Action
     1    | Do nothing.
     2    | Do nothing.
     3    | Stay put (keep looking for treasure).
     4    | Stay put (keep looking for treasure).
     5    | Try to return to camp.

At the end of a day, the following string shall be passed after the last turn's END string, informing everyone on who is alive:
END_DAY [Day #] [Bot 1 Status] [Bot 2 Status]

where the status is a comma separated list of either A (alive) or D (dead). The following day begins immediately after.
The simulation ends when there are fewer than 6 live servants. Your program will receive the following input at the end of the simulation:
EXIT

Rules/Details

Only on turns where your action is S will you find treasure.
Number of simulations run: 1000 times
Your program should not take any more than 1 second to determine moves.
Your program should not exit early; it will be started exactly once.
Make sure that the output buffer (if applicable) is flushed after each output.
Files may be written to in your bot's folder (./players/BotName/). Your bot name is whatever you name your bot, with all non-alphanumeric characters removed and written in CamelCase. Entries may save data between runs of the controller, as runs are done sequentially.
Your program must exit after receiving EXIT.
Programs that fail to compile or throw errors or output invalid text (not in the format of 5 characters separated by commas) may be excluded from the competition. A newline must follow each output.
The controller may be found on GitHub.

Please include the bot name, language+version, code, and command to compile (if applicable) and run your bot.
Example
Text outputted by the program is prefixed here with a >. Your program should not output this character.
INDEX 2
START_DAY 1/3
START_TURN 1
>S,S,S,S,S
END_TURN 1 S,R,S,S,S S,S,S,S,S
START_TURN 2
>S,S,S,S,S
END_TURN 2 S,N,S,R,S S,S,S,S,S
START_TURN 3
>R,R,S,S,S
END_TURN 3 R,N,R,N,R R,R,S,S,S
START_TURN 4
>N,N,S,S,S
END_TURN 4 N,N,N,N,N N,N,S,S,S
START_TURN 5
>N,N,R,R,R
END_TURN 5 N,N,N,N,N N,N,r,r,R
END_DAY 1 A,A,A,A,A A,A,D,D,A
START_DAY 2/3
START_TURN 1
>S,S,N,S,N
END_TURN 1 R,R,R,R,R S,S,D,D,N
END_DAY 2 A,A,A,A,A D,D,D,D,D
EXIT

The scores for the above example are:
Bot#    Day 1   Day 2   Total
1       10      0       10
  S1    1+2     0       3
  S2    0       0       0
  S3    1+2     0       3
  S4    1       0       1
  S5    1+2     0       3

2       20      0       20
  S1    1+2     0       3
  S2    1+2     0       3
  S3    0       0       0
  S4    0       0       0
  S5    1+2+3+8 0       14

The winner is therefore the player, bot 2. Note that the winner does not have to survive to the absolute end. (Also note that the player could have remained until turn 30 on day 1, since the camp would not be full until the player sent one more bot back).
Scores
Bot               Score
Bob               2939.422
Statisticians     2905.833
Morning Birds     1652.325
Evolved           1578.285
Slow Returners    1224.318
Wandering Fools   1065.908
Randomizers       735.313
Drunkards         0
Plague            0

Logs are available on GitHub.
Results per each trial are available on this google spreadsheet.

If a servant doesn't return, is he counted towards the number of people that die this day?

@EagleV_Attnam The day ends either when there are enough servants that have returned, or 30 turns have passed,  in which everyone that hasn't returned will die, regardless of the earlier determined number of deaths.

Right, that was silly, sorry.

If a servant returns to camp, can he deliver treasure found so far and then go out to search again on that same day?

@MikeSweeney No. Once a servant returns, he stays.

Do I understand correctly that the number of competing bots in a simulation is unknown until after the first turn of the first day?

@Zgarb If there are enough bots (4 or more), the number of competing bots can be guessed from the maximum number of servants that may die, passed with START_DAY. Otherwise, yes, the number is unknown until after the first turn.

Hold off running the competition until Tuesday, OK? I've got a bot in the works, but it's taking some time. ;)

@COTO The run that determines the bounty will be done during the grace period of the bounty, so you have plenty of time.

Darn it. I need a few more hours. Not going to make the deadline. >___<

@COTO I'll probably be running the controller around 12 hours from now

@es1024: Thanks for the heads-up. I unfortunately just don't have the time. Work obligations and all. I might still submit a bot "for the heck of it" somewhere down the line, however. Best of luck to all participants. ;)

Bob - C++
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <algorithm>

using namespace std;

int compare(int i, int j)
  {
  if (i < j)
    return (-1);
  if (i == j)
    return (0);
  if (i > j)
    return (1);
  }

int main()
  {
  int index;
  int day;
  int turn;
  int slash_index;
  int to_die;
  int num_alive;
  int mine_alive;
  int turn_to_return;
  bool returned;
  string line;
  vector<int> last_returns;
  vector<int> today_returns;

  getline(cin, line);

  if (line.compare(0, 6, "INDEX ") != 0)
    {
    cerr << "INVALID INDEX LINE \"" << line << "\"" << endl;

    return (-1);
    }

  index = atoi(line.substr(6).c_str()) - 1;

  while (1) // Day loop
    {
    getline(cin, line);
    if (line.compare(0, 4, "EXIT") == 0)
      {
      return (0);
      }
    else if (line.compare(0, 9, "START_DAY") != 0 || (slash_index = line.find('/')) == string::npos)
      {
      cerr << "INVALID START_DAY \"" << line << "\"" << endl;
      return (-1);
      }

    day = atoi(line.substr(10, slash_index - 10).c_str());
    to_die = atoi(line.substr(slash_index + 1, line.length() - slash_index - 1).c_str());

    if (day != 1)
      {
      if (to_die > num_alive)
        {
        turn_to_return = 30;
        }
      else
        {
        turn_to_return = last_returns[last_returns.size() - to_die] - 1;
        }
      }

    returned = false;

    for (turn = 1; turn <= 30; ++turn)
      {
      getline(cin, line);

      if (line.compare(0, 4, "EXIT") == 0)
        {
        return (0);
        }
      if (line.compare(0, 7, "END_DAY") == 0)
        {
        goto end_day;
        }
      if (line.compare(0, 10, "START_TURN") != 0)
        {
        cerr << "INVALID START_TURN \"" << line << "\"" << endl;
        }

      if (day == 1)
        {
        switch (compare(turn, 30))
          {
            case -1:
              cout << "S,S,S,S,S" << endl;
              break;

            case 0:
              cout << "R,R,R,R,R" << endl;
              break;

            case 1:
              cout << "N,N,N,N,N" << endl;
              break;
          }
        }
      else
        {
        if (returned)
          {
          cout << "N,N,N,N,N" << endl;
          }
        /*
        else if (num_alive - today_returns.size() < to_die)
          {
          cout << "R,R,R,R,R" << endl;
          returned = true;
          }
        */
        else if (turn >= turn_to_return)
          {
          cout << "R,R,R,R,R" << endl;
          returned = true;
          }
        else
          {
          cout << "S,S,S,S,S" << endl;
          }
        }

      getline(cin, line);

      if (line.compare(0, 4, "EXIT") == 0)
        {
        return (0);
        }
      if (line.compare(0, 8, "END_TURN") != 0)
        {
        cerr << "INVALID END_TURN \"" << line << "\"" << endl;
        }

      stringstream ss(line);
      string item;
      int i = 0;
      while (getline(ss, item, ' '))
        {
        i++;
        if (i > 2 && i - 3 != index)
          {
          int num_to_add = count(item.begin(), item.end(), 'R'); // Add turn to today_returns for each servant that returned
          for (int j = 0; j < num_to_add; j++)
            {
            today_returns.push_back(turn);
            }
          }
        }

      }

    getline(cin, line);

  end_day:

    if (line.compare(0, 4, "EXIT") == 0)
      {
      return (0);
      }
    else if (line.compare(0, 7, "END_DAY") != 0)
      {
      cerr << "INVALID END_DAY \"" << line << "\"" << endl;
      return (-1);
      }

    stringstream ss(line);
    string item;
    int i = 0;
    num_alive = 0;
    while (getline(ss, item, ' '))
      {
      i++;
      if (i > 2 && i - 3 != index)
        {
        num_alive += count(item.begin(), item.end(), 'A');
        }
      else if (i - 3 == index)
        {
        mine_alive = count(item.begin(), item.end(), 'A');
        }
      }

    last_returns = today_returns;
    today_returns.clear();

    }

  return (0);
  }

To Compile:
g++ -o Bob.exe Bob.cpp

To Run:
./players/Bob/Bob.exe

Statisticians, Python 3
The statisticians always work together. On the first turn, they return to the camp when two thirds of their opponents have done so. On the subsequent turns, they rely on the data they have collected from the previous turns to predict the habits of the other servants, and try to return to the camp at the last safe moment.
Program
# Team of treasure-hunting statisticians
# Run with:
# python3 statisticians.py

num_others = None
running = True
while running:
    msg = input().split()
    msg_type = msg.pop(0)
    if msg_type == "INDEX":
        my_index = int(msg[0])-1
    elif msg_type == "START_DAY":
        day, max_deaths = tuple(map(int, msg[0].split('/')))
    elif msg_type == "START_TURN":
        turn = int(msg[0])
        if day == 1:
            if turn == 1:
                print("S,S,S,S,S")
            elif turn == 30 or num_active <= max_deaths * 4/5:
                print("R,R,R,R,R") # On first day, return when 4/5 of  maximum number of dying servants remain
            else:
                print("S,S,S,S,S")
        elif turn >= 29 or len(expected_servants[turn+1]) <= max(2, max_deaths * 3/4) or len(expected_servants[turn]) <= max(2, max_deaths * 1/4):
            print("R,R,R,R,R") # If many servants are expected to return next turn or someone is sure to die, return to camp
        else:
            print("S,S,S,S,S") # Otherwise, keep going
    elif msg_type == "END_TURN":
        turn = int(msg.pop(0))
        others_moves = [tuple(s.split(',')) for s in msg[:my_index] + msg[my_index+1:]]
        if num_others is None: # End of first turn, initialize variables that depend on number of servants
            num_others = len(others_moves)
            others_history = [{} for i in range(num_others)]
        if day == 1:
            num_active = sum([move.count('S') for move in others_moves])
        for i, moves in enumerate(others_moves): # Log the return habits of other bots
            if turn == 1:
                others_history[i][day] = [0]*5
            for j, move in enumerate(moves):
                if move == "R": # Only safely returned servants are taken into account
                    others_history[i][day][j] = turn
                    if day > 1:
                        for future_turn in range(turn, 30):
                            expected_servants[future_turn].discard((i,j))
    elif msg_type == "END_DAY":
        day = int(msg.pop(0))
        my_statuses = tuple(msg[my_index].split(','))
        others_statuses = [tuple(s.split(',')) for s in msg[:my_index] + msg[my_index+1:]]
        expected_servants = [set() for i in range(30)] # Compute the sets of expected servants for each turn
        for i in range(num_others):
            for j in range(5):
                if others_statuses[i][j] == 'A':
                    turn_sum = 0
                    for day_num in others_history[i]:
                        turn_sum += others_history[i][day_num][j]
                    for turn in range(turn_sum//day):
                        expected_servants[turn].add((i,j))
    elif msg_type == "EXIT":
        running = False

As you can see, I shamelessly stole the program structure from @Mike Sweeney.
Command
python3 statisticians.py

EDIT: Fixed a bug in the check for returning home. They should perform somewhat better now.
EDIT 2: The statisticians are now smarter than before: they keep track of which servants have returned to the camp in the current day, and adjust their predictions accordingly. Also, they take more risks, returning to the camp when 3/4 of the maximum number of dying servants remain. This pushes them back to the top (just barely; Bob has become very dangerous).

Drunkards, Perl 5
A bit too much alcohol and they'll never find their way back to camp.
This entry is primarily an example, but will participate.
Program
#!/usr/bin/perl
use 5.10.1;
$| = 1; # disable buffering
@actions = qw(S S S S S);

$_ = <>; ~/^INDEX (\d+)/;
$index = $1;

while(<>){
    if(index($_, 'START_TURN') == 0){
        say join(',', @actions);
    }elsif(index($_, 'END_DAY') == 0){
        # update actions based on who is alive
        # index 1-indexed; first bot at position 2.
        # this is not actually necessary for Drunkards, as all of Drunkards'
        #  servants will die on day 1 in any case.
        # This check is here simply as an example.
        my @status = split(',',(split(' '))[$index + 1]);
        my $i;
        for($i = 0; $i < 5; ++$i){
            # action is S if alive, N if dead. Servants will never be in camp.
            $actions[$i] = $status[$i] eq 'A' ? 'S' : 'N';
        }
    }elsif(index($_, 'EXIT') == 0){
        exit 0;
    }
}

Command
perl ./players/Drunkards/Drunkards.pl

Should your code $status[$i] eq 'A' ? 'S' : 'D'; be $status[$i] eq 'A' ? 'S' : 'N'; to meet the spec?

@MikeSweeney Good catch. I forgot to fix that when I changed the spec while this challenge was still in the sandbox.

Morning Birds
The early bird catches the worm!!!
package players.MorningBirds;

import java.io.*;
import java.util.*;

/*
 * Java 7
 *
 * Compile with "javac ./players/MorningBirds/MorningBirds.java"
 * Run with "java players.MorningBirds.MorningBirds"
 *
 * Servants find treasure from morning until noon.
 * At noon they go to bed to prepare for next day.
 *
 * According to Benjamin Franklin, "Early to bed, early to rise, keeps a
 *      man healthy, WEALTHY, and wise."
 *
 *
 */
public class MorningBirds {

    protected final static String STARTDAY = "START_DAY";

    protected final static String STARTTURN = "START_TURN";

    protected final static String ENDTURN = "END_TURN";

    protected final static String ENDDAY = "END_DAY";

    protected final static String MOVERETURN = "R";

    protected final static String MOVESEARCH = "S";

    protected final static String MOVENOTHING = "N";

    protected final static String RETURNED = "R";

    protected final static String FAILEDRETURN = "r";

    protected final static String SEARCHING = "S";

    protected final static String DEAD = "D";

    protected final static String SLEEPING = "N";

    protected final static String EXIT = "EXIT";

    protected final static String ALIVE = "A";

    protected enum Status{SEARCHING, DEAD, RETURNED}

    protected enum Move{RETURN, SEARCH, NOTHING}

    protected int index;

    protected int day;

    protected int turnNum;

    protected int howManyTeams;

    protected int howManyWillDieTodayAtMost;

    protected int howManyHaveDiedToday;

    protected int howManyEnemyPlayers;

    protected int howManyAliveEnemyPlayers;

    protected int howManyEnemyTeams;

    protected int howManyDeadEnemyPlayers;

    protected int howManyReturnedEnemyPlayers;

    protected int howManySearchingEnemyPlayers;

    protected int howManyTotalPlayers;

    protected int howManyTotalAlivePlayers;

    protected int howManyTotalDeadPlayers;

    protected int howManyTotalReturnedPlayers;

    protected int howManyTotalSearchingPlayers;

    protected int howManyOwnAlivePlayers;

    protected int howManyOwnDeadPlayers;

    protected int howManyOwnReturnedPlayers;

    protected int howManyOwnSearchingPlayers;

    protected Status[] statuses = new Status[5];

    protected Status[][] allStatuses = null;

    protected List<Status[][]> allDayStatuses = null;

    protected List<List<Status[][]>> allTimeStatuses = new ArrayList<>();

    protected BufferedReader in = new BufferedReader(
            new InputStreamReader(System.in));

    public static void main (String args[]) throws Exception{
        new MorningBirds().start();
    }

    public void start() throws Exception{

        index = Integer.parseInt(in.readLine().split("\\s")[1]);
        Arrays.fill(statuses, Status.SEARCHING);

        while(true){
            String[] input = in.readLine().split("\\s");
            if (input[0].equals(ENDTURN) || input[0].equals(ENDDAY)){
                updateStatus(input);
            } else if (input[0].equals(EXIT)){
                return;
            } else if (input[0].equals(STARTDAY)){
                updateDay(input);
            } else if (input[0].equals(STARTTURN)){
                updateTurn(input);
                doTurn(input);
            }

        }

    }

    protected void updateStatus(String[] input){
        if (allStatuses == null && input[0].equals(ENDTURN)){
            allStatuses = new Status[input.length - 2][5];
            for (Status[] enemyStatus : allStatuses){
                Arrays.fill(enemyStatus, Status.SEARCHING);
            }
            howManyTeams = input.length - 2;
            howManyEnemyTeams = input.length - 3;
            howManyTotalPlayers = howManyTeams * 5;
            howManyTotalAlivePlayers = howManyTotalPlayers;
            howManyTotalSearchingPlayers = howManyTotalAlivePlayers;
            howManyAliveEnemyPlayers = howManyTotalPlayers - 5;
            howManyEnemyPlayers = howManyEnemyTeams * 5;
            howManyOwnAlivePlayers = 5;
            howManyOwnSearchingPlayers = 5;
            howManySearchingEnemyPlayers = howManyAliveEnemyPlayers;
        }
        for ( int j = 0; j < howManyTeams; j++){
            String[] stats = input[j + 2].split(",");
            for(int i = 0; i < 5; i++){
                switch (stats[i]){
                    case "R":
                    case "N":
                        if (allStatuses[j][i] != Status.RETURNED){
                            howManyTotalReturnedPlayers++;
                            howManyTotalSearchingPlayers--;
                            if (j == index - 1) {
                                howManyOwnReturnedPlayers++;
                                howManyOwnSearchingPlayers--;
                            } else {
                                howManyReturnedEnemyPlayers++;
                                howManySearchingEnemyPlayers--;
                            }
                        }
                        allStatuses[j][i] = Status.RETURNED;
                        break;
                    case "A":
                    case "S":
                        if (allStatuses[j][i] != Status.SEARCHING){
                            howManyTotalReturnedPlayers--;
                            howManyTotalSearchingPlayers++;
                            if (j == index - 1) {
                                howManyOwnReturnedPlayers--;
                                howManyOwnSearchingPlayers++;
                            } else {
                                howManyReturnedEnemyPlayers--;
                                howManySearchingEnemyPlayers++;
                            }
                        }
                        allStatuses[j][i] = Status.SEARCHING;
                        break;
                    case "r":
                    case "D":
                        if (allStatuses[j][i] != Status.DEAD){
                            howManyTotalAlivePlayers--;
                            howManyTotalDeadPlayers++;
                            howManyHaveDiedToday++;
                            howManyTotalSearchingPlayers--;
                            if (j == index - 1){
                                howManyOwnAlivePlayers--;
                                howManyOwnDeadPlayers++;
                                howManyOwnSearchingPlayers--;
                            } else {
                                howManyAliveEnemyPlayers--;
                                howManyDeadEnemyPlayers++;
                                howManySearchingEnemyPlayers--;
                            }
                        }
                        allStatuses[j][i] = Status.DEAD;
                        break;
                    default:
                        break;
                }
            }
        }
        statuses = allStatuses[index - 1];
        if (input[0].equals(ENDTURN)){
            allDayStatuses.add(allStatuses.clone());
        }
        if (input[0].equals(ENDDAY)){
            Status[][] statusesToAdd = new Status[howManyTeams][5];
            for (int i = 0; i < statusesToAdd.length; i++){
                for (int j = 0; j < statusesToAdd[i].length; j++){
                    if (allStatuses[i][j] == Status.SEARCHING){
                        statusesToAdd[i][j] = Status.RETURNED;
                    } else {
                        statusesToAdd[i][j] = Status.DEAD;
                    }
                }
            }
            while (turnNum <= 30){
                allDayStatuses.add(statusesToAdd.clone());
                turnNum++;
            }
            allTimeStatuses.add(allDayStatuses);
        }
    }

    protected void updateDay(String[] input) throws Exception{
        day = Integer.parseInt(input[1].split("/")[0]);
        howManyWillDieTodayAtMost = Integer.parseInt(input[1].split("/")[1]);
        howManyHaveDiedToday = 0;
        allDayStatuses = new ArrayList<>();
        if (day == 1){
            Arrays.fill(statuses, Status.SEARCHING);
            howManyOwnAlivePlayers = 5;
            howManyOwnSearchingPlayers = 5;
        }
    }

    protected void updateTurn(String[] input){
        turnNum = Integer.parseInt(input[1]);
    }

    protected void doTurn(String[] input){
        Move[] moves = new Move[5];
        for (int i = 0; i < 5; i++){
            if (statuses[i] == Status.DEAD ||
                        statuses[i] == Status.RETURNED) {
                moves[i] = Move.NOTHING;
                continue;
            } else {
                moves[i] = doMove(i);
            }
        }
        String[] outputs = new String[5];
        for (int i = 0; i < 5; i++){
            switch (moves[i]){
                case SEARCH:
                    outputs[i] = MOVESEARCH;
                    break;
                case RETURN:
                    outputs[i] = MOVERETURN;
                    break;
                case NOTHING:
                    outputs[i] = MOVENOTHING;
            }
        }
        String totalOutput = "";
        for(String output : outputs){
            if (totalOutput != ""){
                totalOutput += ",";
            }
            totalOutput += output;
        }
         System.out.println(totalOutput);
    }

    //Implement this method differently for different
    //strategies.
    public Move doMove(int playerNumber){
        if (turnNum >= 15){
            return Move.RETURN;
        }
        return Move.SEARCH;
    }

    /**
     * Returns the status of one of your players.
     * Your players have numbers 1 to 5 inclusive.
     * Throws exception if number is outside range.
     *
     */
    protected Status getStatus(int player){
        if (player > 5 || player < 1){
            throw new IllegalArgumentException(
                    "getStatus(" + player +") failed.");
        }
        return statuses[player - 1];
    }

    /**
     * Returns the status of a player in a team.
     * Team numbers start with 1 inclusive.
     * Players have numbers 1 to 5 inclusive.
     * Throws exception if argument player is outside range.
     * Throws exception if argument team is less than 1 or is greater
     * than the number of teams.
     * Returns Status.SEARCHING if day == 1 and turnNum == 1 and argument
     * team >= 1.
     */
    protected Status getStatus(int team, int player){
        if (team < 1 || player < 1 || player > 1 ||
                (team > howManyTeams && day == 1 && turnNum == 1)){
            throw new IllegalArgumentException(
                    "getStatus(" + team + ", " + player + ") failed.");
        }
        if (day == 1 && turnNum == 1 && team >= 1){
            return Status.SEARCHING;
        }
        return allStatuses[team - 1][player - 1];
    }

    /**
     * Returns the status of a player in a team at the end of argument
     * turn.
     * Team numbers start with 1 inclusive.
     * Players have numbers 1 to 5 inclusive.
     * Turns have numbers 0 to 30 inclusive.
     * Status at turn 0 is equal to status at start of turn 1.
     * Throws exception if argument turn hasn't happened yet.
     * Throws exception if argument player is outside range.
     * Throws exception if argument team is less than 1 or is greater
     * than the number of teams.
     */
    protected Status getStatus(int turn, int team, int player){
        if (turn == 0){
            if (day == 1){
                return Status.SEARCHING;
            } else {
                return getStatus(day - 1, 30, team, player);
            }
        }
        if (turnNum <= turn || turn < 0|| player > 5 || player < 1 ||
                team < 1 || team > howManyTeams){
            throw new IllegalArgumentException("getStatus(" + turn +
                    ", " + team + ", " + player + ") failed.");
        }
        return allDayStatuses.get(turn - 1)[team - 1][player - 1];
    }

    /**
     * Returns the status of a player in a team at the end of argument
     * turn on the day of argument day.
     * Team numbers start with 1 inclusive.
     * Players have numbers 1 to 5 inclusive.
     * Turns have numbers 0 to 30 inclusive.
     * Days have numbers 1 inclusive and up.
     * Status at turn 0 is equal to status at start of turn 1.
     * Throws exception if argument day hasn't ended yet or is less
     * than one.
     * Throws exception if argument turn is out of range.
     * Throws exception if argument player is outside range.
     * Throws exception if argument team is less than 1 or is greater
     * than the number of teams.
     */
    protected Status getStatus(int day, int turn, int team, int player){
        if (turn == 0){
            if (day == 1){
                return Status.SEARCHING;
            } else {
                return getStatus(day - 1, 30, team, player);
            }
        }
        if (this.day <= day || day < 1 || turn > 30 || turn < 0 ||
                player > 5 || player < 1 ||
                team < 1 || team > howManyTeams){
            throw new IllegalArgumentException("getStatus(" + day + ", "
                    + turn + ", " + team + ", " + player + ") failed.");
        }
        return allTimeStatuses.get(day - 1).get(turn - 1)[team - 1][player - 1];
    }

}

Edit: Made it so anyone could easily subclass it. Just redefine doMove(int playerNumber) for your own bot. I have added several helpful fields and methods. I have extensively tested it. It does not save the statuses from previous simulations. Please tell me if there are any problems.
Compile with: javac ./players/MorningBirds/MorningBirds.java
Run with: java players.MorningBirds.MorningBirds

Would it be okay if I made the methods and variables protected and later made a subclass of this for the challenge?

Feel free to use multiple source files if necessary, or reuse code from other entries, as long as entries are not working together.

@es1024 In experimenting I noticed that a bot dies if it does nothing all day from turn 1. Is that intended?

A bot that never returns (R) on any given day will always die that day.

The controller becomes unresponsive if I add players SlowReturners and Randomizers. Note: Sorry I'm posting comments here. I do not have the reputation needed to post elsewhere.

That's likely because the ruby solutions don't output a newline or flush the buffer as they need to; I've added a comment about this on those solutions.

Randomizers - Ruby
Just to mess up statistics driven bots, the randomizers are quite unpredictable. All of them do return at once, at a random turn in an attempt to strand others.
(Not influenced by other players.)
def min(a,b);(a<b)?a:b;end
x=""
r=0
while x != "EXIT"
  x=gets.chomp
  if x =~ /^START_DAY/
    r = min(rand(30),rand(30))
  end
  if x =~ /^START_TURN (\d*)/
    puts ($1.to_i>r)?'R,R,R,R,R':'S,S,S,S,S'
  end
end

Evolved
I used Genetic Programming (through JGAP) to make this bot. It came up with a simple answer that beats all others (barely).
package players.Evolved;

import players.MorningBirds.*;
import java.util.*;

public class Evolved extends MorningBirds{

    List<Integer> scrambled = new ArrayList<>();

    public static void main(String[] args) throws Exception{
        new Evolved().start();
    }

    public Evolved() throws Exception{
        super();
    }

    @Override
    public MorningBirds.Move doMove(int playerNum){
        if (!(howManyTotalSearchingPlayers < (turnNum - getScrambled(index)))){
            return Move.SEARCH;
        } else {
            return Move.RETURN;
        }
    }

    @Override
    protected void updateStatus(String[] input){
        super.updateStatus(input);
        if (input[0].equals(ENDTURN) && (Integer.parseInt(input[1]) == 1)){
            for (int i = 1; i <= howManyTeams; i++){
                scrambled.add(i);
            }
            Collections.shuffle(scrambled);
        }
    }

    public int getScrambled(int in){
        if (in > scrambled.size() || in < 1 ){
            return in;
        }
        return scrambled.get(in - 1);
    }
}

Compile with: javac players/Evolved/Evolved.java
Run with: java players.Evolved.Evolved
Edit: Grrr... Bob messed me up!!!
Edit: Yay!!! Bob, got killed by a nasty plague!!!

Wandering Fools, Python 2
This is a simple Python bot that sends out the servants until a preset "goback" time is reached, then they try to enter camp and stay until the next day.
It is also a basic framework for more complex bots that others may wish to use. It is, however, untested with the judge engine, so let me know if I have made an error.
Program
import sys
from random import randint, choice
team = range(5)

while True:
    inp = sys.stdin.readline().split()
    cmd = inp.pop(0)
    if cmd == 'INDEX':
        teamnum = int(inp[0]) - 1   # using zero based indexing
    elif cmd == 'START_DAY':
        daynum, deadnum = [int(v) for v in inp[0].split('/')]
        # Set up strategy for the day:
        goback = [randint(5,25) for i in team]
    elif cmd == 'START_TURN':
        turn = int(inp[0])
        # Output actions [R]eturn, [S]earch, [N]othing here:
        actions = ['S' if turn < goback[i] else 'R' for i in team]
        sys.stdout.write( (','.join(actions)) + '\n' )
        sys.stdout.flush()
    elif cmd == 'END_TURN':
        endturn = int(inp.pop(0))
        status = [v.split(',') for v in inp]  # R,r,S,D,N
        # [R]eturned, [r]ejected, [S]earching, [D]ead, [N]othing
        mystatus = status[teamnum]
    elif cmd == 'END_DAY':
        endturn = int(inp.pop(0))
        alive = [v.split(',') for v in inp]  # [A]live or [D]ead
        myalive = alive[teamnum]
    elif cmd == 'EXIT':
        sys.exit(0)

Command
python WanderingFools.py

Edit: Changed action deciding code after rule clarification.

Plague
Plague is a disease. It is not rational. It is predictable. Diseases cannot collect treasure, nor do they care for treasure. Plague makes other players sick. The wise ones stay home and forget about treasure. The foolish ones are always foolish and will never get much treasure. Evolved is (fortunately) immune to Plague. He is also wise. He goes and collects treasure, and does not die.
package players.Plague;

import players.MorningBirds.MorningBirds;

public class Plague extends MorningBirds{

    public static void main(String[] args) throws Exception{
        new Plague().start();
    }

    public Plague() throws Exception{
        super();
    }

    @Override
    public MorningBirds.Move doMove(int playerNum){
        if (day > howManyTotalDeadPlayers){
            return Move.SEARCH;
        } else {
            return Move.RETURN;
        }
    }
}

Compile with: javac players/Plague/Plague.java
Run with: java players.Plague.Plague
Bob and Statisticians are now resistant to plague.

hmm...when I run this bot it always dies on the first day...

I used a genetic algorithm to make this. It should die on the second day. It messes up statistic driven bots so that they perform quite badly compared to Evolved.

SlowReturners - Ruby
Sends one servant back every 5 turns.
x=""
while x != "EXIT"
  x=gets.chomp
  if x =~ /^START_TURN (\d*)/
    puts (1..5).map{|i|(i<=$1.to_i/5)?"R":"S"}.join(",")
  end
end

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

authors: Азнабай Искандароа

authors: Владимир Дымов

sort: votes


text:
Write a C / C++ Polyglot
This challenge's concept is pretty simple. All you have to do is write a program that will compile as both valid C and valid C++! Well, there are some catches. The program must behave differently when compiled in each language. The program must have different output for each language in order to be considered "behaving differently".
Rules

The program must be both valid C and C++
The program must have different outputs based on the language it was compiled in.
#ifdef __cplusplus or other "easy" preprocessor tricks are discouraged! (Other preprocessor operations are perfectly fine, though.)
Try not to make it look completely obvious that the program does something different.

This is a popularity-contest, so whoever has the most interesting and surprising solution wins. Have fun!
Example:
I created my own program to see if this was even possible to do with out #ifdef tricks:
#include <stdio.h>
#include <string.h>

char *m="C++ rules!";

int t[11]={0,0,0,0,1,-1,-3,9,-8,82,0};

char tr(char c,int i)
{
    return c+((sizeof('!')+1)&1)*t[i];
}

int main()
{
    int i = 0;
    for(;i<strlen(m);i++)
    {
        printf("%c",tr(m[i],i));
    }
    printf("\n");
    return 0;
}

This program outputs C++ rules! when compiled in C++ and C++ stinks when compiled in C.
Explanation:

 What causes the difference between languages is the tr() function. It takes advantage of one of the differences between C and C++, specifically, how char literals are treated. In C, they are treated as integers, so sizeof('!') returns 4, as opposed to 1 in C++. The ((...+1)&1) part is just part of a simple bitwise operation that will return 1 if sizeof('!') returns 4, and 0 if it returns 1. That resulting number is multiplied by the ints in array t and then that product is finally added to the specific character being transformed. In C++ the product will always be zero, so the string C++ rules! remains unchanged. In C, the product will always be the value in t, and so the string changes to C++ stinks.

I'm sure this is a dupe of something...

@BetaDecay Is it? I tried searching for something similar and I couldn't find anything.

Can you please explain how your program works differently (if it doesn't spoil the challenge)?

@A.L I edited in an explanation to my post.

All the ones from http://stackoverflow.com/questions/2038200/write-a-program-that-will-print-c-if-compiled-as-an-ansi-c-program-and-c/ could be used here - with a little obfuscation.

Is the cake a lie?
As there has been much debate over whether the cake is or is not a lie, I wrote this program to answer this contentious question.

#include <stdio.h>

// checks if two things are equal
#define EQUALS(a,b) (sizeof(a)==sizeof(b))

struct Cake{int Pie;}; // the cake is a pie!
typedef struct Cake Lie;
main(){
    struct CakeBox{
        struct Cake{ // the cake contains lies!
            Lie Lies[2];
        };
    };
    typedef struct Cake Cake;

    printf("The cake is ");
    if(EQUALS(Cake, Lie)){
        printf("a LIE!\n");
    }else{
        printf("..not a lie?\n");
    }
    return 0;
}

What will the outcome be?
C:

 The cake is ..not a lie?

C++:

 The cake is a LIE!

This. I like this.

Just some bools
#include <stdio.h>

int test(bool)
  {
  return sizeof(bool) == sizeof(int);
  }

int main(void)
  {
  puts(test(0) ? "C" : "C++");
  return 0;
  }
http://codepad.org/dPFou20W
http://codepad.org/Ko6K2JBH

bool is not part of C89

@malat Yep, and exactly this fact is used in this solution.
For c++ the function is
int test(bool /unnamed boolean argument/);
and for C it uses default int declaration wich means
int test(int bool);
so 'bool' is a name of integer variable.

I could have done this with a 3 line program but then it would be obvious why it produces different results for C and C++.  So instead I started writing a bigger program with some stegonography which gets different results in C and C++...
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct product
{
    int quantity;
    char name[20];
    char desc[80];
};

struct _customer
{
    char name[80];
    struct product *products;
} customer;

int main(int argc, char *argv[])
{

struct shipment
{
    char tracking_number[40];
    int quantity;
    struct product { int model; int serial; } sku;
};

struct _supplier
{
    char name[80];
    struct shipment *shipments;
} supplier;

/* now read the command line and allocate all the space we need */

if(argc<5)
{
    printf("Usage: %s <supplier name> <# of shipments> <customer name> <# of products> ",argv[0]);
    exit(1);
}

strcpy(supplier.name,argv[1]);
int shipments_size = atoi(argv[2])*sizeof(struct shipment);
printf("Allocating %d bytes for %s shipments\n", shipments_size,supplier.name);
supplier.shipments=(struct shipment *)malloc(shipments_size);

strcpy(customer.name,argv[3]);
int products_size = atoi(argv[4])*sizeof(struct product);
printf("Allocating %d bytes for %s products\n", products_size,customer.name);

/* ... TODO ... finish the rest of this program later */

free(customer.products);
free(supplier.shipments);

return 0;
}

You need to specify a command line.  When I run it on my copy of gcc I get this output:
>g++ x.cpp

>a.exe "Bob Supplier" 1 "Jane Customer" 1
Allocating 52 bytes for Bob Supplier shipments
Allocating 104 bytes for Jane Customer products

>gcc x.c

>a.exe "Bob Supplier" 1 "Jane Customer" 1
Allocating 52 bytes for Bob Supplier shipments
Allocating 8 bytes for Jane Customer products

How can things go so horribly wrong?

Although others did the same thing, you masked it pretty well.

#include <stdio.h>

int c[1];
int main() {
   struct c { int cpp[2]; };
   printf("%d\n", (int)sizeof(c)/4);
}

This one works with C++11 and newer and any C so far (before C11).
#include <stdio.h>

int main()
{
    auto a = 'a';
    printf(sizeof(a) == sizeof(int) ? "C\n" : "C++\n");
    return 0;
}

See here:
C++: http://ideone.com/9Gkg75
and C: http://ideone.com/eECSmr
It exploits the fact that in C++11 the auto keyword got a new meaning. So while a in C is of type int stored in an AUTOmatic location it is of type char in C++11.
EDIT: As FUZxxl said the implicit int was removed in C11.

Doesn't work with C11 as C11 has removed the implicit int rule.

@FUZxxl Thanks, I adjusted my post.

Self-describing program
This will print "This program is written in C!" if compiled using a C compiler; otherwise, it'll print "This program is written in C++!". It needs a C99 compiler.
#include <stdbool.h>
#include <stdio.h>
char str[] = "This program is written in C++ ";
#define S (sizeof(str)-sizeof(true)-sizeof(true)%4)
int main(){for(int i=S;i<=S+1;++i)str[i]=i==S?'!':'\0';puts(str);return 0;}

 Most other posts take advantage of the difference of the size of a char in C vs C++; this one uses the fact that, in C99, true is defined to be a number. This inserts the exclamation point and null terminator based on the size of true.

#include <stdio.h>

int main() {
  char arr[100];
  printf("%zu",sizeof(0, arr)); // prints 8 in C and 100 in C++
}

In C the comma operator forces an array-to-pointer conversion while in C++ the result of the comma operator:

The type and value of the result are the type and value of the right operand; the result is of the same value category as its right operand,

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/