gistfile1

class mysql-server {
   case $operatingsystem {
      freebsd:   { $pkg_name = 'mysql55-server' $service_name = 'mysql-server' }                                                        
}

Package[$pkg_name] -> Service[$service_name]

   package { $pkg_name :
      ensure => installed,
   }
   service { $service_name :
      require => Package[$pkg_name],
      ensure  => running,
      enable  => true,
    }
}