First stab at lexical scalar aliases

No \my$x= yet.  Only my $x; \$x =....

It does not work properly with variables closed over from outside;
hence, all the to-do tests fail still, since they do the assign-
ment in evals.

But this much works:

$ ./miniperl -Ilib -Mfeature=:all -e 'my $m; \$m = \$n; warn \$m; warn \$n'
Lvalue references are experimental at -e line 1.
SCALAR(0x7fa04b805510) at -e line 1.
SCALAR(0x7fa04b805510) at -e line 1.

1 files changed, 12 insertions, 1 deletions

diff --git a/pp.c b/pp.c
index 7a34e24ea8..df9085c193 100644
--- a/pp.c
+++ b/pp.c
@@ -6162,7 +6162,18 @@ PP(pp_runcv)
 
 PP(pp_refassign)
 {
-    DIE(aTHX_ "Unimplemented");
+    dSP;
+    dTOPss;
+    if (!SvROK(sv)) DIE(aTHX_ "Assigned value is not a reference");
+    if (SvTYPE(SvRV(sv)) > SVt_PVLV)
+	DIE(aTHX_ "Assigned value is not a scalar reference");
+    SvREFCNT_dec(PAD_SV(ARGTARG));
+    PAD_SETSV(ARGTARG, SvREFCNT_inc_NN(SvRV(sv)));
+    if (PL_op->op_flags & OPf_MOD)
+	SETs(sv_2mortal(newSVsv(sv)));
+    /* XXX else can weak references go stale before they are read, e.g.,
+       in leavesub?  */
+    RETURN;
 }