When localising a magic value, propagate the readonly flag

only if this scalar has \0 magic or has magic without a
'set' method. (follows change #20479 for bug #23141.)
p4raw-link: @20479 on //depot/perl: 33f3c7b8444b48791ad016570a41a23483d750d2

p4raw-id: //depot/perl@21323

1 files changed, 6 insertions, 1 deletions

diff --git a/t/op/local.t b/t/op/local.t
index 5a5b7ee552..28613e7a13 100755
--- a/t/op/local.t
+++ b/t/op/local.t
@@ -1,6 +1,6 @@
 #!./perl
 
-print "1..78\n";
+print "1..79\n";
 
 sub foo {
     local($a, $b) = @_;
@@ -271,3 +271,8 @@ print "ok 77\n";
 eval { for ($1) { local $_ = 1 } };
 print "not " if $@;
 print "ok 78\n";
+
+# The s/// adds 'g' magic to $_, but it should remain non-readonly
+eval { for("a") { for $x (1,2) { local $_="b"; s/(.*)/+$1/ } } };
+print "not " if $@;
+print "ok 79\n";