$use StdIO Class ;

Main = { <Letter? 'A'>;
         <PrintLN 'fail'>;
       },
   
       { <Letter? 23>;
         <PrintLN 'fail: argument is not of symbol type'>;
       },
       { <Letter? 'â'>;
         <PrintLN 'fail'>;
       },

       { <Letter? 'AB'>;
         <PrintLN 'fail: argument is not a symbol'>;
       };