I can't reproduce your results on either an Ubuntu or a Red Hat box.

But that the error message may be misleading: It's what I see if I try your code on a win32 machine.

So, if you're running 'doze, the correct quoting is:

perl -le "2**255;"

      but probably a better way to "see if bignum is found" is to check this way:

perldoc bignum

Update: Duh! Missed the <c>perl -v...<c> in the OP. Nonetheless, using perldoc to test if a module is installed is apt to be less error prone.