sub second {
    my $num_ref = shift;

    my $sum = 0;

    my @newarray = ( 6 .. 10 );

    # try one of these options
    # foreach ( @$num_ref, 6 .. 10 ) {
    foreach ( @$num_ref, @newarray ) {
    $sum += $_;
    }

    return $sum;
}

##</code><code>##

my $result = second( @num );

sub second {
    my ( @array ) = @_;
# etc

##</code><code>##

my $result = second( \@num );

sub second {
    my ( $aref ) = @_;
    my @new_array = @$aref;
    # my $new_ref = [ @$aref ]; # alternative