The default setting is WordSeparators->{" ", "\t"}.
Strings used as word separators may contain several characters.
With the option setting NullWords->False, any number of word separators may appear between any two successive words.
WordSeparators->{{lsep1, ...}, {rsep1, ...}} specifies different left and right separators for words. Words must have a left separator at the beginning, and a right separator at the end, and cannot contain any separators.
Strings given as record separators are automatically taken as word separators.
