diff --git a/ChangeLog b/ChangeLog
index 936bed691e..76b1ba036a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Wed Feb 20 12:41:59 2002  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* hash.c (rb_any_cmp): should handle Qundef in keys.
+
+	* eval.c (remove_method): should not remove a empty method to
+	  implement "undef".
+
+	* eval.c (rb_eval): should allow singleton class def for
+	  true/false/nil.
+
 Tue Feb 19 22:49:29 2002  Minero Aoki  <aamine@loveruby.net>
 
 	* lib/net/http.rb: remove unused class Accumulator.
@@ -10,6 +20,15 @@ Tue Feb 19 22:49:29 2002  Minero Aoki  <aamine@loveruby.net>
 
 	* doc/net/http.rb: modify typo in the description of basic auth.
 
+Tue Feb 19 20:20:12 2002  Ed Sinjiashvili  <edsin@swes.saren.ru>
+
+	* parse.y (str_extend): backslash escape was done wrong.
+
+Tue Feb 19 15:51:41 2002  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* class.c (rb_include_module): should preserve ancestor order in
+	  the included class/module.
+
 Tue Feb 19 14:45:32 2002  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* marshal.c (r_object): complete restoration before calling
diff --git a/class.c b/class.c
index b4d8c935ae..ea3e124293 100644
--- a/class.c
+++ b/class.c
@@ -330,8 +330,10 @@ rb_include_module(klass, module)
 	/* ignore if the module included already in superclasses */
 	for (p = RCLASS(klass)->super; p; p = RCLASS(p)->super) {
 	    if (BUILTIN_TYPE(p) == T_ICLASS) {
-		if (RCLASS(p)->m_tbl == RCLASS(module)->m_tbl)
+		if (RCLASS(p)->m_tbl == RCLASS(module)->m_tbl) {
+		    c = p;
 		    goto skip;
+		}
 	    }
 	}
 	RCLASS(c)->super = include_class_new(module, RCLASS(c)->super);
diff --git a/eval.c b/eval.c
index f2dba3a293..db75fb549b 100644
--- a/eval.c
+++ b/eval.c
@@ -314,7 +314,7 @@ remove_method(klass, mid)
 	rb_raise(rb_eSecurityError, "Insecure: can't remove method");
     }
     if (OBJ_FROZEN(klass)) rb_error_frozen("class/module");
-    if (!st_delete(RCLASS(klass)->m_tbl, &mid, &body)) {
+    if (!st_delete(RCLASS(klass)->m_tbl, &mid, &body) || !body->nd_body) {
 	rb_raise(rb_eNameError, "method `%s' not defined in %s",
 		 rb_id2name(mid), rb_class2name(klass));
     }
@@ -3159,17 +3159,28 @@ rb_eval(self, n)
 	{
 	    VALUE klass;
 
-	    klass = rb_eval(self, node->nd_recv);
-	    if (rb_special_const_p(klass)) {
-		rb_raise(rb_eTypeError, "no virtual class for %s",
-			 rb_class2name(CLASS_OF(klass)));
+	    result = rb_eval(self, node->nd_recv);
+	    if (result == Qtrue) {
+		klass = rb_cTrueClass;
 	    }
-	    if (rb_safe_level() >= 4 && !OBJ_TAINTED(klass))
-		rb_raise(rb_eSecurityError, "Insecure: can't extend object");
-	    if (FL_TEST(CLASS_OF(klass), FL_SINGLETON)) {
-		rb_clear_cache();
+	    else if (result == Qfalse) {
+		klass = rb_cTrueClass;
+	    }
+	    else if (result == Qnil) {
+		klass = rb_cNilClass;
+	    }
+	    else {
+		if (rb_special_const_p(result)) {
+		    rb_raise(rb_eTypeError, "no virtual class for %s",
+			     rb_class2name(CLASS_OF(klass)));
+		}
+		if (rb_safe_level() >= 4 && !OBJ_TAINTED(result))
+		    rb_raise(rb_eSecurityError, "Insecure: can't extend object");
+		if (FL_TEST(CLASS_OF(result), FL_SINGLETON)) {
+		    rb_clear_cache();
+		}
+		klass = rb_singleton_class(result);
 	    }
-	    klass = rb_singleton_class(klass);
 	    
 	    if (ruby_wrapper) {
 		rb_extend_object(klass, ruby_wrapper);
diff --git a/hash.c b/hash.c
index a9abb0fbab..57fe0d1013 100644
--- a/hash.c
+++ b/hash.c
@@ -69,6 +69,7 @@ rb_any_cmp(a, b)
     if (SYMBOL_P(a) && SYMBOL_P(b)) {
 	return a != b;
     }
+    if (a == Qundef || b == Qundef) return -1;
 
     args[0] = a;
     args[1] = b;
diff --git a/parse.y b/parse.y
index 9307b7e144..2594f9be0d 100644
--- a/parse.y
+++ b/parse.y
@@ -3933,7 +3933,7 @@ str_extend(list, term, paren)
 		    tokadd('\\');
 		    tokadd(c);
 		}
-		break;
+		goto loop_again;
 	      case '{':
 		if (brace != -1) brace_nest++;
 	      default:
diff --git a/version.h b/version.h
index f58e7534f8..b8c3fe019d 100644
--- a/version.h
+++ b/version.h
@@ -1,4 +1,4 @@
 #define RUBY_VERSION "1.6.6"
-#define RUBY_RELEASE_DATE "2002-02-19"
+#define RUBY_RELEASE_DATE "2002-02-20"
 #define RUBY_VERSION_CODE 166
-#define RUBY_RELEASE_CODE 20020219
+#define RUBY_RELEASE_CODE 20020220