       ctoken strvar separators
              Parse  a  token  out  of  a  character string.  The
              string to parse is contained in the variable  named
              strvar.   The string separators contains all of the
              valid  separator  characters  for  tokens  in   the
              string.  All leading separators are skipped and the
              first token is returned.  The variable strvar  will
              be  modified to contain the remainder of the string
              following the token.

              This command is provided by Extended Tcl.
