make $1 et al readonly under threads; make C<undef $1> fail like

C<$1 = undef> does

p4raw-id: //depot/perl@2335

1 files changed, 10 insertions, 0 deletions

diff --git a/op.c b/op.c
index cdc93325d6..d98cbd9e98 100644
--- a/op.c
+++ b/op.c
@@ -570,6 +570,16 @@ find_threadsv(char *name)
 	case '`':
 	case '\'':
 	    PL_sawampersand = TRUE;
+	    /* FALL THROUGH */
+	case '1':
+	case '2':
+	case '3':
+	case '4':
+	case '5':
+	case '6':
+	case '7':
+	case '8':
+	case '9':
 	    SvREADONLY_on(sv);
 	    /* FALL THROUGH */