engine/lib/locomotive/regexps.rb

module Locomotive
  module Regexps
    SUBDOMAIN  = /^[a-z][a-z0-9_]*[a-z0-9]{1}$/
    DOMAIN     = /^[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(:[0-9]{1,5})?(\/.*)?$/ix
  end
end