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, 4 insertions, 0 deletions

diff --git a/op.c b/op.c
index 481158db3f..8849369944 100644
--- a/op.c
+++ b/op.c
@@ -5225,6 +5225,10 @@ OP *
 Perl_op_convert_list(pTHX_ I32 type, I32 flags, OP *o)
 {
     if (type < 0) type = -type, flags |= OPf_SPECIAL;
+    if (type == OP_RETURN) {
+        if (FEATURE_MODULE_TRUE_IS_ENABLED)
+            flags |= OPf_SPECIAL;
+    }
     if (!o || o->op_type != OP_LIST)
         o = force_list(o, FALSE);
     else