sub Half
{
    my $n = shift;
    my $SubBody = Power_Of_Two( $n )    ? 
        "return \$_[$[] >> Log2( $n );" :
        "return int( \$_[$[] / $n );";
    my $code = "sub { $SubBody }";
    my $sub = eval $code;
    die "Code '$code' gave error $@" if $@;
    return $sub;
}