Strange problem on 5.1, 5.2, -current.

I've run into a rather interesting problem that I suspect is causing
problems for more people.

We run "rancid", which is software to pull configs from routers.  At
the root, it is an expect script using expect + tcl as installed from
ports.  It spawns a telnet, sends some commands to the remote device,
and saves the output to a file.

We've run this for years on 3.x and 4.x with no problems.  We
recently tried to put it on a 5.2 machine (later testing also on
sparc, and then on 5.1).  What happens is that sometimes a character
returned by the remote device is doubled.

Indeed, the behavior we see is that on subsequent runs output will
cycle like this:

ip classless

to:

ip cclassless

back to:

ip classless

It tends to always happen to the same character for a particular
device, so my guess is there is an off by one error somewhere that
is repeatedly triggered.  The question is, is the problem in FreeBSD,
TCL, Expect, or Rancid.  I've run a few tests on tcl and expect, I
can't trigger the problem.  The FreeBSD box is doing a number of
other things, without showing a problem.

I hate to be this vague, but the only way to repeat it so far is with
the actual full blown setup (although I can do it with that on multiple
versions on multiple boxes) and I'm a bit stumped how to go further. 

If anyone has seen something like this before, or has an idea on how
to troubleshoot I'm all ears.

-- 
       Leo Bicknell - bicknell_at_ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
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