define mypg($ensure = "present") {
        $ver = extlookup($name, "present", "packages")

        @package{$name: ensure => $ver}
}

class vpackages {
        mypg{"ngrep": ensure => present }
}

class ngrep inherits vpackages {
        Mypg["ngrep"] {
                ensure  => absent
        }

        realize(Package["ngrep"])
}

include vpackages
include ngrep