(without or without dot ...)

That would prepend "tex." on all the following parameter names. Config::Param::print_file() could get some smarts to detect common prefixes. And done you are with pseudo-groups.

I could even add [tex.] as alias for that and, when avoiding here-document multiline strings and meta stuff, would have something that should parse as INI.

8. post-3.0.0: $config{hidenonshort}

consider providing a list of those instead ... or in addition, at least