Availability:built-in
pack_attach(+PackDir, 
+Options)- duplicate(+Action)
 - What to do if the same package is already installed in a different 
directory. Action is one of
- warning
 - Warn and ignore the package.
 - keep
 - Silently ignore the package.
 - replace
 - Unregister the existing and insert the new package
 
 - search(+Where)
 - Determines the order of searching package library directories. Default 
is 
last, alternative isfirst.