[perl #114020, #90018, #53186] Make given alias $_

This commit makes given() alias $_ to the argument, using a slot in
the lexical pad if a lexical $_ is in scope, or $'_ otherwise.

This makes it work very similarly to foreach, and eliminates the
problem of List::Util functions not working inside given().

1 files changed, 9 insertions, 2 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index ca953ad05e..cb549fa841 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -4273,8 +4273,15 @@ PP(pp_entergiven)
     ENTER_with_name("given");
     SAVETMPS;
 
-    SAVECLEARSV(PAD_SVl(PL_op->op_targ));
-    sv_setsv_mg(PAD_SV(PL_op->op_targ), POPs);
+    if (PL_op->op_targ) {
+	SAVEPADSVANDMORTALIZE(PL_op->op_targ);
+	SvREFCNT_dec(PAD_SVl(PL_op->op_targ));
+	PAD_SVl(PL_op->op_targ) = SvREFCNT_inc_NN(POPs);
+    }
+    else {
+	SAVE_DEFSV;
+	DEFSV_set(POPs);
+    }
 
     PUSHBLOCK(cx, CXt_GIVEN, SP);
     PUSHGIVEN(cx);