Revert "Deprecate literal unescaped "{" in regexes."

This reverts commit 2a53d33.

Not the entire commit was reverted, but the deprecation message is
gone.  This caused too many problems.  See thread
http://www.nntp.perl.org/group/perl.perl5.porters/2012/11/msg195425.html
(which lists previous threads).

pod/perldiag.pod

@@ -536,9 +536,9 @@ check the return value of your socket() call?  See L<perlfunc/bind>.
 (W unopened) You tried binmode() on a filehandle that was never opened.
 Check your control flow and number of arguments.
 
-=item "\b{" is deprecated; use "\b\{" instead
+=item "\b{" is deprecated; use "\b\{" instead in regex; marked by <-- HERE in m/%s/
 
-=item "\B{" is deprecated; use "\B\{" instead
+=item "\B{" is deprecated; use "\B\{" instead in regex; marked by <-- HERE in m/%s/
 
 (W deprecated, regexp) Use of an unescaped "{" immediately following a
 C<\b> or C<\B> is now deprecated so as to reserve its use for Perl
@@ -5093,18 +5093,6 @@ C<undef *foo>.
 (A) You've accidentally run your script through B<csh> instead of Perl.
 Check the #! line, or manually feed your script into Perl yourself.
 
-=item Unescaped left brace in regex is deprecated, passed through in regex; 
-marked by <-- HERE in m/%s/
-
-(D deprecated, regexp) You used a literal C<"{"> character in a regular 
-expression pattern. You should change to use C<"\{"> instead, because a future 
-version of Perl (tentatively v5.20) will consider this to be a syntax error.  If
-the pattern delimiters are also braces, any matching right brace
-(C<"}">) should also be escaped to avoid confusing the parser, for
-example,
-
-    qr{abc\{def\}ghi}
-
 =item unexec of %s into %s failed!
 
 (F) The unexec() routine failed for some reason.  See your local FSF

regcomp.c

@@ -10165,6 +10165,12 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 	vFAIL("Internal urp");
 				/* Supposed to be caught earlier. */
 	break;
+    case '{':
+	if (!regcurly(RExC_parse)) {
+	    RExC_parse++;
+	    goto defchar;
+	}
+	/* FALL THROUGH */
     case '?':
     case '+':
     case '*':
@@ -10244,6 +10250,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 	    ret = reg_node(pRExC_state, op);
 	    FLAGS(ret) = get_regex_charset(RExC_flags);
 	    *flagp |= SIMPLE;
+	    if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+		ckWARNregdep(RExC_parse, "\"\\b{\" is deprecated; use \"\\b\\{\" instead");
+	    }
 	    goto finish_meta_pat;
 	case 'B':
 	    RExC_seen_zerolen++;
@@ -10255,6 +10264,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 	    ret = reg_node(pRExC_state, op);
 	    FLAGS(ret) = get_regex_charset(RExC_flags);
 	    *flagp |= SIMPLE;
+	    if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+		ckWARNregdep(RExC_parse, "\"\\B{\" is deprecated; use \"\\B\\{\" instead");
+	    }
 	    goto finish_meta_pat;
 
 	case 'D':
@@ -10755,22 +10767,15 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 			/* FALL THROUGH */
 		    default:
 			if (!SIZE_ONLY&& isALPHANUMERIC(*p)) {
-			    ckWARN2reg(p + 1, "Unrecognized escape \\%.1s passed through", p);
+			    /* Include any { following the alpha to emphasize
+			     * that it could be part of an escape at some point
+			     * in the future */
+			    int len = (isALPHA(*p) && *(p + 1) == '{') ? 2 : 1;
+			    ckWARN3reg(p + len, "Unrecognized escape \\%.*s passed through", len, p);
 			}
 			goto normal_default;
 		    }
 		    break;
-		case '{':
-		    /* Currently we don't warn when the lbrace is at the start
-		     * of a construct.  This catches it in the middle of a
-		     * literal string, or when its the first thing after
-		     * something like "\b" */
-		    if (! SIZE_ONLY
-			&& (len || (p > RExC_start && isALPHA_A(*(p -1)))))
-		    {
-			ckWARNregdep(p + 1, "Unescaped left brace in regex is deprecated, passed through");
-		    }
-		    /*FALLTHROUGH*/
 		default:
 		  normal_default:
 		    if (UTF8_IS_START(*p) && UTF) {

t/lib/warnings/regcomp

@@ -59,24 +59,20 @@ Unrecognized escape \m passed through in regex; marked by <-- HERE in m/a\m <--
 use warnings 'regexp'; no warnings "deprecated";
 "foo" =~ /\q/;
 "foo" =~ /\q{/;
-"foo" =~ /\w{/;
 "foo" =~ /a\b{cde/;
 "foo" =~ /a\B{cde/;
 "bar" =~ /\_/;
 no warnings 'regexp';
 "foo" =~ /\q/;
 "foo" =~ /\q{/;
-"foo" =~ /\w{/;
 "foo" =~ /a\b{cde/;
 "foo" =~ /a\B{cde/;
 "bar" =~ /\_/;
 EXPECT
 Unrecognized escape \q passed through in regex; marked by <-- HERE in m/\q <-- HERE / at - line 4.
-Unrecognized escape \q passed through in regex; marked by <-- HERE in m/\q <-- HERE {/ at - line 5.
-Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\q{ <-- HERE / at - line 5.
-Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\w{ <-- HERE / at - line 6.
-Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/a\b{ <-- HERE cde/ at - line 7.
-Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/a\B{ <-- HERE cde/ at - line 8.
+Unrecognized escape \q{ passed through in regex; marked by <-- HERE in m/\q{ <-- HERE / at - line 5.
+"\b{" is deprecated; use "\b\{" instead in regex; marked by <-- HERE in m/a\ <-- HERE b{cde/ at - line 6.
+"\B{" is deprecated; use "\B\{" instead in regex; marked by <-- HERE in m/a\ <-- HERE B{cde/ at - line 7.
 ########
 # regcomp.c [S_regpposixcc S_regclass]
 #

t/re/pat_advanced.t

@@ -1194,7 +1194,6 @@ sub run_tests {
 
     {
         # \, breaks {3,4}
-        no warnings qw{deprecated regexp};
         ok "xaaay"    !~ /xa{3\,4}y/, '\, in a pattern';
         ok "xa{3,4}y" =~ /xa{3\,4}y/, '\, in a pattern';