package Pen;
use strict;
use warnings;
sub new {
    my $class = shift;
    my $self = { };
    bless $self,$class;
}
sub set_token
{
       my $self = shift;
       $self->{token}{$_[0]} = $_[1];
}

sub get_token
{
       my $self = shift;
       return $self->{token}{$_[0]};
}

sub get_token_keys
{
       my $self = shift;
       keys %{$self->{token}};
}
package main;
my $p = new Pen;
$p->set_token( color => 'red');
$p->set_token( price => '10.0');
print $p->get_token( 'color'),"\n";
print join "\t",$p->get_token_keys(),"\n";