diff --git a/array.c b/array.c
index bbf4c1d4c7..e3c331c833 100644
--- a/array.c
+++ b/array.c
@@ -242,7 +242,7 @@ rb_ary_set_shared(VALUE ary, VALUE shared)
 static inline void
 rb_ary_modify_check(VALUE ary)
 {
-    if (OBJ_FROZEN(ary)) rb_error_frozen("array");
+    rb_check_frozen(ary);
     if (!OBJ_UNTRUSTED(ary) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify array");
 }
diff --git a/ext/readline/readline.c b/ext/readline/readline.c
index ac88c84f59..80358debe4 100644
--- a/ext/readline/readline.c
+++ b/ext/readline/readline.c
@@ -43,10 +43,20 @@
 static VALUE mReadline;
 
 #define EDIT_LINE_LIBRARY_VERSION "EditLine wrapper"
+#ifndef USE_INSERT_IGNORE_ESCAPE
+# ifndef HAVE_EDITLINE_READLINE_H
+#  define USE_INSERT_IGNORE_ESCAPE 1
+# else
+#  define USE_INSERT_IGNORE_ESCAPE 0
+# endif
+#endif
 
 #define COMPLETION_PROC "completion_proc"
 #define COMPLETION_CASE_FOLD "completion_case_fold"
 static ID completion_proc, completion_case_fold;
+#if USE_INSERT_IGNORE_ESCAPE
+static ID id_orig_prompt, id_last_prompt, id_ignore_escape;
+#endif
 
 #ifndef HAVE_RL_FILENAME_COMPLETION_FUNCTION
 # define rl_filename_completion_function filename_completion_function
@@ -145,6 +155,81 @@ readline_event(void)
 }
 #endif
 
+#if USE_INSERT_IGNORE_ESCAPE
+static VALUE
+insert_ignore_escape(VALUE self, VALUE prompt)
+{
+    VALUE last_prompt, orig_prompt = rb_attr_get(self, id_orig_prompt);
+    int ignoring = 0;
+    const char *s0, *s, *e;
+    long len;
+    static const char ignore_code[2] = {RL_PROMPT_START_IGNORE, RL_PROMPT_END_IGNORE};
+
+    prompt = rb_str_new_shared(prompt);
+    last_prompt = rb_attr_get(self, id_last_prompt);
+    if (orig_prompt == prompt) return last_prompt;
+    len = RSTRING_LEN(prompt);
+    if (NIL_P(last_prompt)) {
+	last_prompt = rb_str_tmp_new(len);
+    }
+
+    s = s0 = RSTRING_PTR(prompt);
+    e = s0 + len;
+    rb_str_set_len(last_prompt, 0);
+    while (s < e && *s) {
+	switch (*s) {
+	  case RL_PROMPT_START_IGNORE:
+	    ignoring = -1;
+	    rb_str_cat(last_prompt, s0, ++s - s0);
+	    s0 = s;
+	    break;
+	  case RL_PROMPT_END_IGNORE:
+	    ignoring = 0;
+	    rb_str_cat(last_prompt, s0, ++s - s0);
+	    s0 = s;
+	    break;
+	  case '\033':
+	    if (++s < e && *s == '[') {
+		rb_str_cat(last_prompt, s0, s - s0 - 1);
+		s0 = s - 1;
+		while (++s < e && *s) {
+		    if (ISALPHA(*s)) {
+			if (!ignoring) {
+			    ignoring = 1;
+			    rb_str_cat(last_prompt, ignore_code+0, 1);
+			}
+			rb_str_cat(last_prompt, s0, ++s - s0);
+			s0 = s;
+			break;
+		    }
+		    else if (!('0' <= *s && *s <= '9' || *s == ';')) {
+			break;
+		    }
+		}
+	    }
+	    break;
+	  default:
+	    if (ignoring > 0) {
+		ignoring = 0;
+		rb_str_cat(last_prompt, ignore_code+1, 1);
+	    }
+	    s++;
+	    break;
+	}
+    }
+    if (ignoring > 0) {
+	ignoring = 0;
+	rb_str_cat(last_prompt, ignore_code+1, 1);
+    }
+    rb_str_cat(last_prompt, s0, s - s0);
+
+    rb_ivar_set(self, id_orig_prompt, prompt);
+    rb_ivar_set(self, id_last_prompt, last_prompt);
+
+    return last_prompt;
+}
+#endif
+
 static VALUE
 readline_get(VALUE prompt)
 {
@@ -244,10 +329,18 @@ readline_readline(int argc, VALUE *argv, VALUE self)
     char *prompt = NULL;
     char *buff;
     int status;
+    int ignore_escape = 0;
 
     rb_secure(4);
     if (rb_scan_args(argc, argv, "02", &tmp, &add_hist) > 0) {
 	OutputStringValue(tmp);
+#if USE_INSERT_IGNORE_ESCAPE
+	ignore_escape = RTEST(rb_attr_get(mReadline, id_ignore_escape));
+	if (ignore_escape) {
+	    tmp = insert_ignore_escape(self, tmp);
+	    rb_str_locktmp(tmp);
+	}
+#endif
 	prompt = RSTRING_PTR(tmp);
     }
 
@@ -257,6 +350,11 @@ readline_readline(int argc, VALUE *argv, VALUE self)
     rl_prep_terminal(1);
 #endif
     buff = (char*)rb_protect(readline_get, (VALUE)prompt, &status);
+#if USE_INSERT_IGNORE_ESCAPE
+    if (prompt && ignore_escape) {
+	rb_str_unlocktmp(tmp);
+    }
+#endif
     if (status) {
 #if defined HAVE_RL_CLEANUP_AFTER_SIGNAL
         /* restore terminal mode and signal handler*/
@@ -1312,6 +1410,27 @@ username_completion_proc_call(VALUE self, VALUE str)
     return result;
 }
 
+static VALUE
+readline_s_ignore_escape(VALUE self)
+{
+#if USE_INSERT_IGNORE_ESCAPE
+    return RTEST(rb_attr_get(mReadline, id_ignore_escape)) ? Qtrue : Qfalse;
+#elif defined HAVE_EDITLINE_READLINE_H
+    return Qtrue;
+#else
+    return Qfalse;
+#endif
+}
+
+static VALUE
+readline_s_ignore_escape_set(VALUE self, VALUE flag)
+{
+#if USE_INSERT_IGNORE_ESCAPE
+    rb_ivar_set(mReadline, id_ignore_escape, RTEST(flag) ? Qtrue : Qfalse);
+#endif
+    return flag;
+}
+
 void
 Init_readline()
 {
@@ -1383,6 +1502,18 @@ Init_readline()
     rb_define_singleton_method(mReadline, "refresh_line",
 			       readline_s_refresh_line, 0);
 
+#if USE_INSERT_IGNORE_ESCAPE
+    rb_define_singleton_method(mReadline, "ignore_escape",
+			       readline_s_ignore_escape, 0);
+    rb_define_singleton_method(mReadline, "ignore_escape=",
+			       readline_s_ignore_escape_set, 1);
+
+    CONST_ID(id_orig_prompt, "orig_prompt");
+    CONST_ID(id_last_prompt, "last_prompt");
+    CONST_ID(id_ignore_escape, "ignore_escape");
+    rb_ivar_set(mReadline, id_ignore_escape, Qtrue);
+#endif
+
     history = rb_obj_alloc(rb_cObject);
     rb_extend_object(history, rb_mEnumerable);
     rb_define_singleton_method(history,"to_s", hist_to_s, 0);
diff --git a/gc.c b/gc.c
index b011f4a1c3..99aacdb3d5 100644
--- a/gc.c
+++ b/gc.c
@@ -2677,7 +2677,7 @@ static VALUE
 undefine_final(VALUE os, VALUE obj)
 {
     rb_objspace_t *objspace = &rb_objspace;
-    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
+    rb_check_frozen(obj);
     if (finalizer_table) {
 	st_data_t data = obj;
 	st_delete(finalizer_table, &data, 0);
@@ -2703,7 +2703,7 @@ define_final(int argc, VALUE *argv, VALUE os)
     st_data_t data;
 
     rb_scan_args(argc, argv, "11", &obj, &block);
-    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
+    rb_check_frozen(obj);
     if (argc == 1) {
 	block = rb_block_proc();
     }
diff --git a/hash.c b/hash.c
index 0d1898313b..873219a433 100644
--- a/hash.c
+++ b/hash.c
@@ -248,7 +248,7 @@ rb_hash_dup(VALUE hash)
 static void
 rb_hash_modify_check(VALUE hash)
 {
-    if (OBJ_FROZEN(hash)) rb_error_frozen("hash");
+    rb_check_frozen(hash);
     if (!OBJ_UNTRUSTED(hash) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify hash");
 }
diff --git a/misc/ruby-mode.el b/misc/ruby-mode.el
index 0072f1e0d5..9a21c485a9 100644
--- a/misc/ruby-mode.el
+++ b/misc/ruby-mode.el
@@ -451,8 +451,12 @@ The variable ruby-indent-level controls the amount of indentation.
                (or (eq (char-syntax (char-before (point))) ?w)
                    (ruby-special-char-p))))
         nil)
-       ((and (eq option 'heredoc) (< space 0)) t)
-       ((or (looking-at ruby-operator-re)
+       ((and (progn (goto-char start) (eq option 'heredoc))
+	     (progn (forward-word -1)
+		    (not (and (or (bolp) (not (eq (char-before (point)) ?_)))
+			      (looking-at "class<<")))))
+	t)
+       ((or (progn (goto-char start) (looking-at ruby-operator-re))
             (looking-at "[\\[({,;]")
             (and (looking-at "[!?]")
                  (or (not (eq option 'modifier))
diff --git a/object.c b/object.c
index 5ad5680d88..7eecf49bfc 100644
--- a/object.c
+++ b/object.c
@@ -712,9 +712,7 @@ rb_obj_taint(VALUE obj)
 {
     rb_secure(4);
     if (!OBJ_TAINTED(obj)) {
-	if (OBJ_FROZEN(obj)) {
-	    rb_error_frozen("object");
-	}
+	rb_check_frozen(obj);
 	OBJ_TAINT(obj);
     }
     return obj;
@@ -733,9 +731,7 @@ rb_obj_untaint(VALUE obj)
 {
     rb_secure(3);
     if (OBJ_TAINTED(obj)) {
-	if (OBJ_FROZEN(obj)) {
-	    rb_error_frozen("object");
-	}
+	rb_check_frozen(obj);
 	FL_UNSET(obj, FL_TAINT);
     }
     return obj;
@@ -768,9 +764,7 @@ rb_obj_untrust(VALUE obj)
 {
     rb_secure(4);
     if (!OBJ_UNTRUSTED(obj)) {
-	if (OBJ_FROZEN(obj)) {
-	    rb_error_frozen("object");
-	}
+	rb_check_frozen(obj);
 	OBJ_UNTRUST(obj);
     }
     return obj;
@@ -789,9 +783,7 @@ rb_obj_trust(VALUE obj)
 {
     rb_secure(3);
     if (OBJ_UNTRUSTED(obj)) {
-	if (OBJ_FROZEN(obj)) {
-	    rb_error_frozen("object");
-	}
+	rb_check_frozen(obj);
 	FL_UNSET(obj, FL_UNTRUSTED);
     }
     return obj;
diff --git a/string.c b/string.c
index efb0481937..daabb97a46 100644
--- a/string.c
+++ b/string.c
@@ -350,14 +350,6 @@ str_mod_check(VALUE s, const char *p, long len)
     }
 }
 
-static inline void
-str_frozen_check(VALUE s)
-{
-    if (OBJ_FROZEN(s)) {
-	rb_raise(rb_eRuntimeError, "string frozen");
-    }
-}
-
 size_t
 rb_str_capacity(VALUE str)
 {
@@ -1250,7 +1242,7 @@ str_modifiable(VALUE str)
     if (FL_TEST(str, STR_TMPLOCK)) {
 	rb_raise(rb_eRuntimeError, "can't modify string; temporarily locked");
     }
-    if (OBJ_FROZEN(str)) rb_error_frozen("string");
+    rb_check_frozen(str);
     if (!OBJ_UNTRUSTED(str) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify string");
 }
@@ -1335,7 +1327,7 @@ void
 rb_str_associate(VALUE str, VALUE add)
 {
     /* sanity check */
-    if (OBJ_FROZEN(str)) rb_error_frozen("string");
+    rb_check_frozen(str);
     if (STR_ASSOC_P(str)) {
 	/* already associated */
 	rb_ary_concat(RSTRING(str)->as.heap.aux.shared, add);
@@ -3546,7 +3538,7 @@ rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
                 repl = rb_obj_as_string(repl);
             }
 	    str_mod_check(str, p, len);
-	    str_frozen_check(str);
+	    rb_check_frozen(str);
 	}
 	else {
 	    repl = rb_reg_regsub(repl, str, regs, pat);
diff --git a/struct.c b/struct.c
index f0a377c211..78f836f8f5 100644
--- a/struct.c
+++ b/struct.c
@@ -151,7 +151,7 @@ static VALUE (*const ref_func[])(VALUE) = {
 static void
 rb_struct_modify(VALUE s)
 {
-    if (OBJ_FROZEN(s)) rb_error_frozen("Struct");
+    rb_check_frozen(s);
     if (!OBJ_UNTRUSTED(s) && rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't modify Struct");
 }
diff --git a/transcode.c b/transcode.c
index 17bad37e27..cd4829f291 100644
--- a/transcode.c
+++ b/transcode.c
@@ -2711,9 +2711,7 @@ str_encode_bang(int argc, VALUE *argv, VALUE str)
     VALUE newstr;
     int encidx;
 
-    if (OBJ_FROZEN(str)) { /* in future, may use str_frozen_check from string.c, but that's currently static */
-	rb_raise(rb_eRuntimeError, "string frozen");
-    }
+    rb_check_frozen(str);
 
     newstr = str;
     encidx = str_transcode(argc, argv, &newstr);
diff --git a/variable.c b/variable.c
index ce5c2b8258..46717e73c4 100644
--- a/variable.c
+++ b/variable.c
@@ -1043,7 +1043,7 @@ rb_ivar_set(VALUE obj, ID id, VALUE val)
 
     if (!OBJ_UNTRUSTED(obj) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify instance variable");
-    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
+    rb_check_frozen(obj);
     switch (TYPE(obj)) {
       case T_OBJECT:
         iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
@@ -1305,7 +1305,7 @@ rb_obj_remove_instance_variable(VALUE obj, VALUE name)
 
     if (!OBJ_UNTRUSTED(obj) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify instance variable");
-    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
+    rb_check_frozen(obj);
     if (!rb_is_instance_id(id)) {
 	rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
     }
@@ -1653,8 +1653,7 @@ rb_const_remove(VALUE mod, ID id)
 
     if (!OBJ_UNTRUSTED(mod) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't remove constant");
-    if (OBJ_FROZEN(mod)) rb_error_frozen("class/module");
-
+    rb_check_frozen(mod);
     if (!RCLASS_IV_TBL(mod) || !st_delete(RCLASS_IV_TBL(mod), &n, &v)) {
 	if (rb_const_defined_at(mod, id)) {
 	    rb_name_error(id, "cannot remove %s::%s",
@@ -1819,14 +1818,7 @@ mod_av_set(VALUE klass, ID id, VALUE val, int isconst)
 
     if (!OBJ_UNTRUSTED(klass) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't set %s", dest);
-    if (OBJ_FROZEN(klass)) {
-	if (BUILTIN_TYPE(klass) == T_MODULE) {
-	    rb_error_frozen("module");
-	}
-	else {
-	    rb_error_frozen("class");
-	}
-    }
+    rb_check_frozen(klass);
     if (!RCLASS_IV_TBL(klass)) {
 	RCLASS_IV_TBL(klass) = st_init_numtable();
     }
@@ -2075,8 +2067,7 @@ rb_mod_remove_cvar(VALUE mod, VALUE name)
     }
     if (!OBJ_UNTRUSTED(mod) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't remove class variable");
-    if (OBJ_FROZEN(mod)) rb_error_frozen("class/module");
-
+    rb_check_frozen(mod);
     if (RCLASS_IV_TBL(mod) && st_delete(RCLASS_IV_TBL(mod), &n, &val)) {
 	return (VALUE)val;
     }
diff --git a/vm.c b/vm.c
index 084c30964a..27185f6786 100644
--- a/vm.c
+++ b/vm.c
@@ -1858,10 +1858,7 @@ vm_define_method(rb_thread_t *th, VALUE obj, ID id, VALUE iseqval,
 		     rb_id2name(id), rb_obj_classname(obj));
 	}
 
-	if (OBJ_FROZEN(obj)) {
-	    rb_error_frozen("object");
-	}
-
+	rb_check_frozen(obj);
 	klass = rb_singleton_class(obj);
 	noex = NOEX_PUBLIC;
     }
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 75e0f91b36..236b3fd3f5 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1298,9 +1298,8 @@ vm_setivar(VALUE obj, ID id, VALUE val, IC ic)
     if (!OBJ_UNTRUSTED(obj) && rb_safe_level() >= 4) {
 	rb_raise(rb_eSecurityError, "Insecure: can't modify instance variable");
     }
-    if (OBJ_FROZEN(obj)) {
-	rb_error_frozen("object");
-    }
+    
+    rb_check_frozen(obj);
 
     if (TYPE(obj) == T_OBJECT) {
 	VALUE klass = RBASIC(obj)->klass;
diff --git a/vm_method.c b/vm_method.c
index a76277c81d..41c53a5b47 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -211,10 +211,8 @@ rb_method_entry_make(VALUE klass, ID mid, rb_method_type_t type,
 		rb_class2name(rb_ivar_get(klass, attached)));
 	mid = ID_ALLOCATOR;
     }
-    if (OBJ_FROZEN(klass)) {
-	rb_error_frozen("class/module");
-    }
 
+    rb_check_frozen(klass);
     mtbl = RCLASS_M_TBL(klass);
 
     /* check re-definition */
@@ -463,8 +461,7 @@ remove_method(VALUE klass, ID mid)
     if (rb_safe_level() >= 4 && !OBJ_UNTRUSTED(klass)) {
 	rb_raise(rb_eSecurityError, "Insecure: can't remove method");
     }
-    if (OBJ_FROZEN(klass))
-	rb_error_frozen("class/module");
+    rb_check_frozen(klass);
     if (mid == object_id || mid == id__send__ || mid == idInitialize) {
 	rb_warn("removing `%s' may cause serious problems", rb_id2name(mid));
     }