# foo.pm
package foo;

# class variables (not object instance variables)
our %defaults = (bar=>0, foo=>7);

# a couple typical object methods
sub initialize {
    my $this = shift;
    $this->{instance_variable} = $defaults{bar};
}

sub status {
    my $this = shift;
    return $this->{instance_variable};
}

# a class method
sub set_default_bar {
   $defaults{bar} = shift;
}

# etc...