From b2b95e4c717e3e7005a2a533840bce801ccf74bb Mon Sep 17 00:00:00 2001
From: Father Chrysostomos <sprout@cpan.org>
Date: Sat, 4 Jun 2011 13:10:41 -0700
Subject: [PATCH] Stop localised ties from becoming ro when COW

---
 mg.c       |  2 +-
 t/op/tie.t | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/mg.c b/mg.c
index af2c647..bdded26 100644
--- a/mg.c
+++ b/mg.c
@@ -536,7 +536,7 @@ Perl_mg_localize(pTHX_ SV *sv, SV *nsv, bool setmagic)
 			    mg->mg_ptr, mg->mg_len);
 
 	/* container types should remain read-only across localization */
-	SvFLAGS(nsv) |= SvREADONLY(sv);
+	if (!SvIsCOW(sv)) SvFLAGS(nsv) |= SvREADONLY(sv);
     }
 
     if (SvTYPE(nsv) >= SVt_PVMG && SvMAGIC(nsv)) {
diff --git a/t/op/tie.t b/t/op/tie.t
index b485f62..0b53b14 100644
--- a/t/op/tie.t
+++ b/t/op/tie.t
@@ -1014,3 +1014,19 @@ print "ok\n";
 
 EXPECT
 ok
+########
+#
+# Localising a tied COW scalar should not make it read-only.
+
+sub TIESCALAR { bless [] }
+sub FETCH { __PACKAGE__ }
+sub STORE {}
+tie $x, "";
+"$x";
+{
+    local $x;
+    $x = 3;
+}
+print "ok\n";
+EXPECT
+ok
-- 
1.8.3.1