Apps on port 80

[Croydon]

Although this is also a configuration / installation topic, I think it is better posted in here, so:

I tried to set the app-vhost to port 80, because I just wanted to use a different host name for it but no special port.
This works as far as the config file (apps vhost) is written correctly but the apache cannot restart afterwards as the app vhost file contains a Listen directive.

{vhost_port_listen} Listen {apps_vhost_port}

Does the config template system allow to specify something like:
if port != 80 && port != 443 then {vhost_port_listen} Listen {apps_vhost_port}
endif

so that if one specifies port 80 or port 443 the Listen part is not written?
I think this should then be part of the master conf.