It could be this:

[  7076] By: jhi                                   on 2000/09/14  14:4
+2:56
        Log: Fix for a parsing bug, not for the original bug.

             Subject: Re: [ID 20000910.005] Another segfault with rege
+xes.
             From: Spider Boardman <spider@web.zk3.dec.com>
             Date: Wed, 13 Sep 2000 17:52:20 -0400
             Message-Id: <200009132152.RAA24029@leggy.zk3.dec.com>
     Branch: perl
           ! regcomp.c
[download]

But there are loads of changes in reg*.c between 5.6.0 and 5.6.1 ....

/J\