$ perl -wle 'print log (10**-4950)'
    -11397.7067720196325
    $ perl -wle 'print log (10**-4951)'
    Can't take log of 0 at -e line 1.
    $ perl -wle 'print log (10**-4951 * 100)'
    Can't take log of 0 at -e line 1.