$overloaded .= $x: don't stringify $x

RT #132385

This is a variant of the ($ref . $overloaded) bug which was fixed with
v5.27.5-195-gb3ab0375cb.

Basically, when the overloaded concat method is called, it should pass
$x as-is, rather than as "$x". This fixes PDL-2.018

1 files changed, 13 insertions, 0 deletions

diff --git a/pp_hot.c b/pp_hot.c
index d1d02257ed..7609638b8f 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -661,6 +661,19 @@ PP(pp_multiconcat)
                  */
                 assert(!targ_chain);
                 dsv = newSVpvn_flags("", 0, SVs_TEMP);
+
+                if (   svpv_end == svpv_buf + 1
+                       /* no const string segments */
+                    && aux[PERL_MULTICONCAT_IX_LENGTHS].ssize == -1
+                ) {
+                    /* special case $overloaded .= $arg1:
+                     * avoid stringifying $arg1.
+                     * Similar to the $arg1 . $arg2 case in phase1
+                     */
+                    svpv_end--;
+                    SP--;
+                }
+
                 goto phase3;
             }
         }