package MyPkg;

my @Instances; # Visibility restricted to package by lexical declaration

sub new {
    my $self = shift;
    my $opts = ref $_[0] ? shift : { @_ };
    push @Instances, { %$opts };
    return bless \(my $me = $#Instances), $self;
}

sub getScore {
    my $self = shift;
    return $Instances[$$self]->{score};
}

##</code><code>##

package SomeClass;

sub classMethod {
    my $self = shift;
    die("Not an object/instance method") if ref $self;
    .
    .
}

sub objMethod {
    my $self = shift;
    die("Not an class method") unless ref $self;
    .
    .
}