e H is defined as follows:

       *  If

          -  H is the host domain name of a host; and,

          -  H has the form A.B; and

          -  A has no embedded (that is, interior) dots; and

          -  B has at least one embedded dot, or B is the string "local".
             then the reach of H is .B.

       *  Otherwise, the reach of H is H.

    >>> reach("www.acme.com")
    '.acme.com'
    >>> reach("acme.com")
    'acme.com'
    >>> reach("acme.local")
    '.local'

    r