diff -up perl-5.10.1/ext/re/t/regop.t.git perl-5.10.1/ext/re/t/regop.t
--- perl-5.10.1/ext/re/t/regop.t.git	2009-12-21 19:31:07.564141841 +0100
+++ perl-5.10.1/ext/re/t/regop.t	2009-12-21 19:31:55.158142088 +0100
@@ -233,12 +233,12 @@ anchored "ABC" at 0
 #Freeing REx: "(\\.COM|\\.EXE|\\.BAT|\\.CMD|\\.VBS|\\.VBE|\\.JS|\\.JSE|\\."......
 %MATCHED%
 floating ""$ at 3..4 (checking floating)
-1:1[1] 3:2[1] 5:2[64] 45:83[1] 47:84[1] 48:85[0]
-stclass EXACTF <.> minlen 3
-Found floating substr ""$ at offset 30...
-Does not contradict STCLASS...
-Guessed: match at offset 26
-Matching stclass EXACTF <.> against ".exe"
+#1:1[1] 3:2[1] 5:2[64] 45:83[1] 47:84[1] 48:85[0]
+#stclass EXACTF <.> minlen 3
+#Found floating substr ""$ at offset 30...
+#Does not contradict STCLASS...
+#Guessed: match at offset 26
+#Matching stclass EXACTF <.> against ".exe"
 ---
 #Compiling REx "[q]"
 #size 12 nodes Got 100 bytes for offset annotations.
@@ -258,4 +258,4 @@ Got 100 bytes for offset annotations.
 Offsets: [12]
 1:1[3] 3:4[0]
 %MATCHED%        
-Freeing REx: "[q]"
\ No newline at end of file
+Freeing REx: "[q]"
diff -up perl-5.10.1/regcomp.c.git perl-5.10.1/regcomp.c
--- perl-5.10.1/regcomp.c.git	2009-12-21 19:32:05.893141719 +0100
+++ perl-5.10.1/regcomp.c	2009-12-21 19:33:35.106141384 +0100
@@ -2820,13 +2820,16 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_
                                 }
                             } else {
 /* 
-    Currently we assume that the trie can handle unicode and ascii
-    matches fold cased matches. If this proves true then the following
-    define will prevent tries in this situation. 
-    
-    #define TRIE_TYPE_IS_SAFE (UTF || optype==EXACT)
-*/
+    Currently we do not believe that the trie logic can
+    handle case insensitive matching properly when the
+    pattern is not unicode (thus forcing unicode semantics).
+    If/when this is fixed the following define can be swapped
+    in below to fully enable trie logic.
 #define TRIE_TYPE_IS_SAFE 1
+
+*/
+#define TRIE_TYPE_IS_SAFE (UTF || optype==EXACT)
+
                                 if ( last && TRIE_TYPE_IS_SAFE ) {
                                     make_trie( pRExC_state, 
                                             startbranch, first, cur, tail, count, 
diff -up perl-5.10.1/regexec.c.git perl-5.10.1/regexec.c
--- perl-5.10.1/regexec.c.git	2009-12-21 19:33:50.570141632 +0100
+++ perl-5.10.1/regexec.c	2009-12-21 19:36:41.300142175 +0100
@@ -1006,16 +1006,15 @@ Perl_re_intuit_start(pTHX_ REGEXP * cons
 
 #define REXEC_TRIE_READ_CHAR(trie_type, trie, widecharmap, uc, uscan, len,  \
 uvc, charid, foldlen, foldbuf, uniflags) STMT_START {                       \
-    UV uvc_unfolded = 0;						    \
     switch (trie_type) {                                                    \
     case trie_utf8_fold:                                                    \
 	if ( foldlen>0 ) {                                                  \
-	    uvc_unfolded = uvc = utf8n_to_uvuni( uscan, UTF8_MAXLEN, &len, uniflags ); \
+	    uvc = utf8n_to_uvuni( uscan, UTF8_MAXLEN, &len, uniflags ); \
 	    foldlen -= len;                                                 \
 	    uscan += len;                                                   \
 	    len=0;                                                          \
 	} else {                                                            \
-	    uvc_unfolded = uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN, &len, uniflags ); \
+	    uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN, &len, uniflags ); \
 	    uvc = to_uni_fold( uvc, foldbuf, &foldlen );                    \
 	    foldlen -= UNISKIP( uvc );                                      \
 	    uscan = foldbuf + UNISKIP( uvc );                               \
@@ -1054,9 +1053,6 @@ uvc, charid, foldlen, foldbuf, uniflags)
 		charid = (U16)SvIV(*svpp);                                  \
 	}                                                                   \
     }                                                                       \
-    if (!charid && trie_type == trie_utf8_fold && !UTF) {		    \
-	charid = trie->charmap[uvc_unfolded];			    	    \
-    }								    	    \
 } STMT_END
 
 #define REXEC_FBC_EXACTISH_CHECK(CoNd)                 \