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 example:

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

See also "exp" for the inverse operation.