title: Is regular expression recognition of an email address hard?
body: <p>I recently read somewhere that writing a regexp to match an email address, taking into account all the variations and possibilities of the standard is extremely hard and is significantly more complicated than what one would initially assume.</p>
  <p>Why is that?</p>
  <p>Are there any known and proven regexps that actually do this fully?</p>
  <p>What are some good alternatives to using regexps for matching email addresses?</p>