use strict;
use warnings;

package MyClass;

sub new
{
    my $class = shift;

    my $self = bless {}, $class;

    $self->_init(@_);

    return $self;
}

sub _init
{
    my $self = shift;

    $self->{foo} = 'bar';

    return;
}

sub greet
{
    my ($self, $msg) = @_;

    print "$msg - $self->{foo}\n";

    return;
}

1;

package main;

my $obj = MyClass->new;

$obj->greet("Hello");

1;