Remains as defined in Common Lisp, but see *handle-existing-defpackage* for an extension.
defpackage is as defined in the ANSI standard, with the inclusion of the
:add-use-defaults keyword. However, the standard explicitly declines to define what
defpackage does if a package named defined-package-name already exists and is in a state that differs from that described by the
One non-standard option is supported.
:add-use-defaults, with a true argument, causes the package defined-package-name to inherit from the following packages (as well as any explicitly specified by the
LispWorks User Guide and Reference Manual - 20 Sep 2017