          unset name ?name name ...?
               Remove  one or more variables.  Each name is a variable
               name, specified in any of the ways  acceptable  to  the
               set  command.   If  a  name  refers to an element of an
               array, then that element is removed  without  affecting
               the  rest of the array.  If a name consists of an array
               name with no parenthesized index, then the entire array
               is  deleted.  The unset command returns an empty string
               as result.  An error occurs if  any  of  the  variables
               doesn't exist, or if any of the variables has an active
               trace.
