From the documentation of log:

log EXPR
       log     Returns the natural logarithm (base e) of EXPR.
               If EXPR is omitted, returns log of $_.  To get the
               log of another base, use basic algebra: The base-N
               log of a number is equal to the natural log of
               that number divided by the natural log of N. For exampl
+e:

                   sub log10 {
                       my $n = shift;
                       return log($n)/log(10);
                   }

               See also "exp" for the inverse operation.
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Please check your documentation more thoroughly - this was only a perldoc -f log away.

CU
Robartes-