This is why people get class_eval and instance_eval confused in Ruby. You create class methods with instance eval and instance methods with class eval.

confusing.rb

class Foo
  instance_eval <<-end_eval, __FILE__, __LINE__
    def bar
      "class method"
    end
  end_eval
  
  class_eval <<-end_eval, __FILE__, __LINE__
    def bar
      "instance method"
    end
  end_eval
end

puts Foo.bar # class method
puts Foo.new.bar # instance method