Here is what i think I will change the documentation to say:
"WhateverDBI_SecretKey"
Specifies the secret key for this auth scheme. This should be a long
random string. This should be secret; either make the httpd.conf
file only readable by root, or put the PerlSetVar in a file only
readable by root and include it.
This is required and has no default value. (NOTE: In AuthCookieDBI
versions 1.22 and earlier the secret key either could be set in the
configuration file itself or it could be place in a seperate file
with the path configured with "PerlSetVar
WhateverDBI_SecretKeyFile".
As of version 2.0 you must use "WhateverDBI_SecretKey" and not
"PerlSetVar WhateverDBI_SecretKeyFile".
If you want to put the secret key in a separate file then you can
create a separate file that uses "PerlSetVar WhateverDBI_SecretKey"
and include that file in your main Apache configuration using
Apaches' "Include" directive. You might wish to make the file not
world-readable. Also, make sure that the Perl environment variables
are not publically available, for example via the /perl-status
handler.) See also "COMPATIBILITY" in this man page.