Ripped from Fedora

--- grep-2.5.1/lib/posix/regex.h.oi	2004-01-05 12:09:12.984391131 +0000
+++ grep-2.5.1/lib/posix/regex.h	2004-01-05 12:09:24.717990622 +0000
@@ -109,6 +109,10 @@
    If not set, \{, \}, {, and } are literals.  */
 #define RE_INTERVALS (RE_HAT_LISTS_NOT_NEWLINE << 1)
 
+/* If this bit is set, then ignore case when matching.
+   If not set, then case is significant.  */
+#define RE_ICASE (RE_INVALID_INTERVAL_ORD << 1)
+
 /* If this bit is set, +, ? and | aren't recognized as operators.
    If not set, they are.  */
 #define RE_LIMITED_OPS (RE_INTERVALS << 1)
--- grep-2.5.1/src/search.c.oi	2004-01-05 12:07:00.550199415 +0000
+++ grep-2.5.1/src/search.c	2004-01-05 12:07:00.566197505 +0000
@@ -31,7 +31,7 @@
 
 #include "system.h"
 #include "grep.h"
-#include "regex.h"
+#include <regex.h>
 #include "dfa.h"
 #include "kwset.h"
 #include "error.h"
@@ -190,7 +190,7 @@
   size_t total = size;
   char const *motif = pattern;
 
-  re_set_syntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE);
+  re_set_syntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE | (match_icase ? RE_ICASE : 0));
   dfasyntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE, match_icase, eolbyte);
 
   /* For GNU regex compiler we have to pass the patterns separately to detect
@@ -268,12 +268,12 @@
 
   if (strcmp (matcher, "awk") == 0)
     {
-      re_set_syntax (RE_SYNTAX_AWK);
+      re_set_syntax (RE_SYNTAX_AWK | (match_icase ? RE_ICASE : 0));
       dfasyntax (RE_SYNTAX_AWK, match_icase, eolbyte);
     }
   else
     {
-      re_set_syntax (RE_SYNTAX_POSIX_EGREP);
+      re_set_syntax (RE_SYNTAX_POSIX_EGREP | (match_icase ? RE_ICASE : 0));
       dfasyntax (RE_SYNTAX_POSIX_EGREP, match_icase, eolbyte);
     }