Can you tell me where I'm wrong?

Const
     t: set of char = ['a'..'z','A'..'Z','0'..'9',':',';','-
','!','?','.',',',' ','>','<'];

Var
   l: byte;
   ch: char;
   r: array [1..80] of char;

Begin
     l:= 0;
     fillchar(r,sizeof(r),' ');
     While (not eof(input)) do
           begin
           read(input,ch);
           if (ch in t) then
              begin
              Inc(l);
              case ch of
                   '<': Dec(l,2);
                   '>': ;
                   else r[l]:= ch;
                   end;
              if (l>80) or (l<0) then l:= 0;
              end;
           end;
     write(output,r);
End.