email_regex.rb

EmailAddress = begin
   qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]'
   dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]'
   atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-' +
     '\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+'
   quoted_pair = '\\x5c[\\x00-\\x7f]'
   domain_literal = "\\x5b(?:#{dtext}|#{quoted_pair})*\\x5d"
   quoted_string = "\\x22(?:#{qtext}|#{quoted_pair})*\\x22"
   domain_ref = atom
   sub_domain = "(?:#{domain_ref}|#{domain_literal})"
   word = "(?:#{atom}|#{quoted_string})"
   domain = "#{sub_domain}(?:\\x2e#{sub_domain})*"
   local_part = "#{word}(?:\\x2e#{word})*"
   addr_spec = "#{local_part}\\x40#{domain}"
   pattern = /\A#{addr_spec}\z/
 end