rep: procedure options (main); /* 5 May 2015 */
   declare s bit (10) varying;
   declare (i, k) fixed binary;

main_loop:
   do s = '1001110011'b, '1110111011'b, '0010010010'b, '1010101010'b,
          '1111111111'b, '0100101101'b, '0100100'b, '101'b, '11'b, '00'b, '1'b;
      k = length(s);
      do i = k/2 to 1 by -1;
         if substr(s, 1, i) = substr(s, i+1, i) then
            do;
               put skip edit (s, ' is a rep-string containing ', substr(s, 1, i) ) (a);
               iterate main_loop;
            end;
      end;
      put skip edit (s, ' is not a rep-string') (a);
   end;

end rep;