Ruby Error with in the Regex

gistfile1.rb

require 'digest' #for password hasing
class User < ActiveRecord::Base
	
#It tells Ruby to create reader and writer methods for password. Because the password
#column doesn’t exist in your table anymore, a password method isn’t created automatically
#by Active Record. Still, you need a way to set the password before it’s encrypted, so you make
#your own attribute to use. This works like any model attribute, except that it isn’t persisted to
#the database when the model is saved.
attr_accessor :password

validates_uniqueness_of :email
validates_length_of :email, :within => 5..50
validates :email, :uniqueness => true,
 :length => { :within => 5..50 },
 :format => { :with => /^[^@][\w.-]+@[\w.-]+[.][a-z]{2,4}$/i }

validates_confirmation_of :password
validates_length_of :password, :within => 4..20
validates_presence_of :password, :if => :password_required?
#And it’s
#required only if this is a new record (the hashed_password attribute is blank) or if the password
#accessor you created has been used to set a new password (password.present?)


has_one :profile
has_many :articles, -> { order('published_at DESC, title ASC') },
 :dependent => :nullify
has_many :replies, :through => :articles, :source => :comments

#applies to all operations that trigger a save, including create and update.
before_save :encrypt_new_password

def self.authenticate(email, password)
 user = find_by_email(email)
 return user if user && user.authenticated?(password)
end


#This is a simple predicate method that checks to make sure the stored
#hashed_password matches the given password after it has been encrypted (via encrypt). If it
#matches, #true is returned.

def authenticated?(password)
 self.hashed_password == encrypt(password)
end

protected
def encrypt_new_password
return if password.blank?
 self.hashed_password = encrypt(password)
end
#which returns true if a password is required or false if it’s not
def password_required?
 hashed_password.blank? || password.present?
end

# for PRODUCTIONO use bcrypt gem (https://github.com/codahale/bcrypt-ruby) instead of SHA1.
def encrypt(string)
 Digest::SHA1.hexdigest(string)
end

end

user= User.first
ArgumentError: The provided regular expression is using multiline anchors (^ or $), which may present a security risk. Did you mean to use \A and \z, or forgot to add the :multiline => true option?
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/format.rb:46:in `check_options_validity'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/format.rb:20:in `check_validity!'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validator.rb:143:in `initialize'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/with.rb:87:in `new'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/with.rb:87:in `block in validates_with'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/with.rb:86:in `each'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/with.rb:86:in `validates_with'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/validates.rb:119:in `block in validates'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/validates.rb:109:in `each'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activemodel-4.0.1/lib/active_model/validations/validates.rb:109:in `validates'
	from /home/guinslym/Documents/programming/rails_book/ch4/blog/app/models/user.rb:13:in `<class:User>'
	from /home/guinslym/Documents/programming/rails_book/ch4/blog/app/models/user.rb:2:in `<top (required)>'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:424:in `load'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:424:in `block in load_file'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:616:in `new_constants_in'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:423:in `load_file'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:324:in `require_or_load'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:463:in `load_missing_constant'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:184:in `const_missing'
	from (irb):8
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.1/lib/rails/commands/console.rb:90:in `start'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.1/lib/rails/commands/console.rb:9:in `start'
	from /home/guinslym/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.1/lib/rails/commands.rb:62:in `<top (required)>'
	from bin/rails:4:in `require'
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