sub new {
    my $class = shift;
    my ( $name ) = @_;
    my $self = bless {
        name       => $name,
        handle_in  => \*STDIN,
        handle_out => \*STDOUT,
    }, $class;
    ...
}

sub __print_readline {
    my ( $self, ... ) = @_;
    ...
    print { $self->{handle_out} } $string;
    ...
}