UnionExpr

# File lib/rexml/parsers/xpathparser.rb, line 492
      def UnionExpr path, parsed
        n = []
        rest = PathExpr( path, n )
        if rest != path
          while rest =~ /^\s*(\|)\s*/
            n = [ :union, n, [] ]
            rest = PathExpr( $', n[-1] )
          end
        end
        if parsed.size == 0 and n.size != 0
          parsed.replace( n )
        elsif n.size > 0
          parsed << n
        end
        rest
      end