```ruby
module Librarian
  class Dsl
    class Receiver

      def initialize(target)
        singleton_class = class << self; self end
        singleton_class.class_eval do
          define_method(target.dependency_name) do |*args, &block|
            target.dependency(*args, &block)
          end
          define_method(:source) do |*args, &block|
            target.source(*args, &block)
          end
          target.source_types.each do |source_type|
            name = source_type[0]
            define_method(name) do |*args, &block|
              target.source(name, *args, &block)
            end
          end
        end
      end

      def run(specfile = nil)
        if block_given?
          instance_eval(&Proc.new)
        else
          case specfile
          when Specfile
            instance_eval(specfile.path.read, specfile.path.to_s, 1)
          when String
            instance_eval(specfile)
          when Proc
            instance_eval(&specfile)
          end
        end
      end

    end
  end
end
```

Use eval with a binding rather than instance_eval when evaluating a string.
user
```ruby
module Librarian
  class Dsl
    class Receiver

      def initialize(target)
        singleton_class = class << self; self end
        singleton_class.class_eval do
          define_method(target.dependency_name) do |*args, &block|
            target.dependency(*args, &block)
          end
          define_method(:source) do |*args, &block|
            target.source(*args, &block)
          end
          target.source_types.each do |source_type|
            name = source_type[0]
            define_method(name) do |*args, &block|
              target.source(name, *args, &block)
            end
          end
        end
      end

      def run(specfile = nil)
        if block_given?
          instance_eval(&Proc.new)
        else
          case specfile
          when Specfile
            eval(specfile.path.read, instance_binding, specfile.path.to_s, 1)
          when String
            eval(specfile, instance_binding)
          when Proc
            instance_eval(&specfile)
          end
        end
      end

      def instance_binding
        binding
      end

    end
  end
end
```
assistant