package foo;
sub new{
    my $class = shift;
    my $base = shift;
    return bless { base_class => $base }, $class;
}
sub write{
    my $self = shift;
    my $base = $self->{base_class};
    print eval "\$self->$base\::read";
}

##</code><code>##

no strict 'refs';
print $self->&{"$base\::read"};  # syntax error

# string found where operator expected
print $self->"$base\::read";

# executes but ignores $base's inheritance, if any
no strict 'refs';
print &{"$base\::read"}( $self );

##</code><code>##

# code above package foo unchanged

package foo::alpha;
BEGIN { @foo::alpha::ISA = qw( foo alpha ); }

package foo::beta;
BEGIN { @foo::beta::ISA = qw( foo beta ); }

package foo;
sub new{
    my $class = shift;
    my $base = shift;
    return bless {}, "$class\::$base";
}

# all other code unchanged