It's called a bug fix. From the Changes file:

[ 13881] By: jhi                                   on 2001/12/24  23:4
+7:53
        Log: Subject: PATCH: Restore "Can't declare scalar dereference
+ in my" error
             From: Mark-Jason Dominus <mjd@plover.com>
             Date: Mon, 24 Dec 2001 18:14:48 -0500
             Message-ID: <20011224231448.25826.qmail@plover.com>
     Branch: perl
           ! op.c t/op/eval.t
[download]

This construct only worked from 5.005_62 until 5.7.2.

Abigail