Interesting responses. I'll tell you the two issues that brought me to writing this e-mail.
1) A long time ago when I was teaching at a company and told people to install some CPAN module, during installation it wanted to open a port on their computer to run the test. Some of the students were were surprised / shocked on the security implications.
As I understand they had their firewall on their computer and the module would not test itself without this.
We used the LAN in their lab which is considered less secure than their internal LAN. Besides this could happen while I am on the road on a public network.
I am not sure what module was that, or if Dancer2 shows this behavior during installation but this issue stuck in my head.
2) I was looking at Flask and it by default it listens to localhost only but right in the quickstart guide they show how to open
Now that I read the response of Warren, I was reminded that actually the fact that Dancer was listening to the outside world on my production server bothered me, but then again, when I try to set it up on a remote server first I always want to make sure that the Dancer application (maybe with Starman) answers me and it is much more convenient if it listens to the outside world. So I am not sure which one would I prefer.
Actually I think I know what I'd like, regardless the defaults: I'd like the default configuration files to contain commented out entries for every (or every important) parameter with short explanation and/or with link to the longer explanation.