# The set for the characters gets changed :
  [A-Za-z0-9 ,"&-']

  # and the RE then looks like this :
  /^[A-Za-z0-9 ,"&-']{4,16}$/

  # and we can modify the RE, so that A-Z also matches
  # a-z with the "i"-modifyer :
  /^[A-Z0-9 ,"&-']{4,16}$/i

  # or equivalent

  /^[a-z0-9 ,"&-']{4,16}$/i