I'd guess perl 5.8.0 on a Redhat Linux box.

By default, Redhat sets the locale environment variables to something like

LANG="en_US.UTF-8"
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Unfortunately, that makes 5.8.0 treat all streams as unicode, which is a bad choice (and corrected in the 5.8.1 release candidates).

Change your profile to set LANG=en_US, and the problem should go away.

If I have the OS and perl version right, that is...
--
Mike