if TRUE, remove variables that start with a dot(.).
verbose
if TRUE, report all removed items.
PBSsave
if TRUE, do not remove .PBSmod.
pos
The pos argument can specify the environment in which to look
for the object in any of several ways: as an integer (the position in
the search list); as the character string name of an element in the
search list; or as an environment (including using sys.frame to access
the currently active function calls).