question about substr

Hi

(1) When I run

               select 1 from dual where '1       '  = substr('21',2,1)
           no result return.   There is  spaces in the left operand.



      (2) When I run

               select 1 from dual where '1        '  = substr('21',
2,1) || '        '
           1 result return



      (3) And  when I run

               select 1 from dual where '1        ' =  '1'
           1 result return

      What is the difference between (1)and(3)?
      Can I find a better method than (2) , so I can eaily compare
without counting the spaces in '1        '

       Thanks.