From: Ralph Shnelvar Date: 2009-11-27T05:46:06+09:00 Subject: Re: Pattern match to fail if two periods in a row >>> "abc..def" !~ /\.\./ =>> false I don't think that "abc..def" !~ /\.\./ is a regular expression. /\.\./ is a regular expression. Basically ... I need something that will work in a Rails validates_format_of # Reject if the email address has two periods in a row validates_format_of :email, # See http://en.wikipedia.org/wiki/E-mail_address :with => ????, :message => 'invalid email format'