You probably wrote something like : print (log(1000) / log(10)) % 3 Which, has stated in perlop, actually means (print (log(1000 / log(10))) % 3.

So you print (log 100)/(log 10) (and the result of this operation is rounded to 3), and then do a modulo operation on the output of print, which doesn't make much sense.

Edit: if that is what happened, use warnings would have given you the answer