sub kfmrunden_bignum {
    my( $num, $pos ) = @_;

    my $bignum = Math::BigFloat->new( $num );
#    $pos = ( $bignum->length )[1] unless defined $pos; # huch, was hab ich mir denn dabei gedacht?!
    $pos ||= 0;

    return 0 + $bignum->ffround( -$pos, 'common' )->bstr;
} # kfmrunden_bignum