$self->{myhash} = {};

##</code><code>##

package MyClass;

sub new {
    my $class = shift;
    my $self = { @_ };
    $self->{myhash} = {};
    return bless $self, $class;
}

sub set_attr {
    my $self = shift;
    my ($key, $val) = @_;
    $self->{myhash}{$key} = $val;
}

sub get_attr {
    my $self = shift;
    my $key  = shift;
    return $self->{myhash}{$key};
}

package main;

my $obj = MyClass->new();

$obj->set_attr( foo => "bar" );

print $obj->get_attr("foo"), "\n";

##</code><code>##

package MyClass;

sub new {
    my $class = shift;
    my $self = { @_ };
    return bless $self, $class;
}

sub set_attr {
    my $self = shift;
    my ($key, $val) = @_;
    $self->{$key} = $val;
}

sub get_attr {
    my $self = shift;
    my $key  = shift;
    return $self->{$key};
}

...