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;