[perl #113470] Constant folding for pack

This takes the pessimistic approach of skipping it for any first argu-
ment that is not a plain non-magical PV, just in case there is a 'p'
or 'P' in the stringified form.

Otherwise it scans the PV for 'p' or 'P' and skips the folding if either
is present.

Then it falls through to the usual op-filtering logic.

I nearly made ‘pack;’ crash, so I added a test to bproto.t.

1 files changed, 1 insertions, 1 deletions

diff --git a/opcode.h b/opcode.h
index 217cb56481..2c7db8383a 100644
--- a/opcode.h
+++ b/opcode.h
@@ -1847,7 +1847,7 @@ EXTCONST U32 PL_opargs[] = {
 	0x00024401,	/* hslice */
 	0x00004b00,	/* boolkeys */
 	0x00091480,	/* unpack */
-	0x0002140d,	/* pack */
+	0x0002140f,	/* pack */
 	0x00111408,	/* split */
 	0x0002140d,	/* join */
 	0x00002401,	/* list */