Applies the statements from the specified policy
definition and then returns control the current
policy statement. Note that the called policy may
itself call other policies (subject to
implementation limitations). This is intended to
provide a policy 'subroutine' capability. The
called policy should contain an explicit or a
default route disposition that returns an
effective true (accept-route) or false
(reject-route), otherwise the behavior may be
ambiguous and implementation dependent