Enable `use feature 'module_true'`

Per RFC 18, whenever `use feature 'module_true';` is enabled in a scope,
any file required with `require` has an implicit return value of true
and will not trigger the "did not return a true value" error condition.

This includes logic to use the OPf_SPECIAL flag for OP_RETURN listops to
indicate that the module_true feature is in effect when it executes.
This flag plays no role unless the OP_RETURN tail calls the pp_leaveeval
logic, so it doesn't affect normal sub returns.

1 files changed, 1 insertions, 0 deletions

diff --git a/op.h b/op.h
index ec3e1204a3..12f0c5ce2d 100644
--- a/op.h
+++ b/op.h
@@ -161,6 +161,7 @@ Deprecated.  Use C<GIMME_V> instead.
                                 /*  On OP_DUMP, has no label */
                                 /*  On OP_UNSTACK, in a C-style for loop */
                                 /*  On OP_READLINE, it's for <<>>, not <> */
+                                /*  On OP_RETURN, module_true is in effect */
 /* There is no room in op_flags for this one, so it has its own bit-
    field member (op_folded) instead.  The flag is only used to tell
    op_convert_list to set op_folded.  */