here we go

manifests/init.pp

@@ -1,4 +1,6 @@
-class varnish {
+class varnish (
+  $listen_port = '80',
+  $cache       = 'malloc,1500m') {
   package { 'varnish': require => Class['packages::backports'], }
 
   # ncsa loggin:
@@ -10,7 +12,8 @@ class varnish {
 
   file {
     '/etc/default/varnish':
-      content => template('varnish/etc_default_varnish.erb'),
+      content => template('varnish/etc_default_varnish.erb');
+
       notify => Service['varnish'];
 
     '/etc/default/varnishnsca':

templates/etc_default_varnish.erb

@@ -45,14 +45,13 @@ MEMLOCK=82000
 # one content server selected by the vcl file, based on the request.  Use a 1GB
 # fixed-size cache file.
 #
-DAEMON_OPTS="-a :80 \
+DAEMON_OPTS="-a :<%= @listen_port %> \
              -T localhost:6082 \
              -f /etc/varnish/default.vcl \
              -S /etc/varnish/secret \
-             -s malloc,1500m \
+             -s <%= @cache %> \
              -p thread_pool_min=500 -p thread_pool_max=2048 \
              -p session_max=10000"
-        
          #-s file,/var/lib/varnish/$INSTANCE/varnish_storage.bin,1G"
 
 ## Alternative 3, Advanced configuration