begin
  _1=:a;_2=:a;_3=:a;_4=:a;_5=:a
  ^~ _1 is reserved for numbered parameters
        ^~ _2 is reserved for numbered parameters
              ^~ _3 is reserved for numbered parameters
                    ^~ _4 is reserved for numbered parameters
                          ^~ _5 is reserved for numbered parameters
  _6=:a;_7=:a;_8=:a;_9=:a;_10=:a
  ^~ _6 is reserved for numbered parameters
        ^~ _7 is reserved for numbered parameters
              ^~ _8 is reserved for numbered parameters
                    ^~ _9 is reserved for numbered parameters
end