gistfile1.txt

use v6;

unit module App::insucalc;

subset Dir of IO::Handle where *.d;

sub MAIN( Dir :$root = $*HOME.child('.insucalc') ) is export {
    App::insucalc::Runner.new( :root($root) ).run();
}

class App::insucalc::Runner {
    my class App::insulcalc::Plan { }
    my class App::insulcalc::Scenario { }

    has Dir $!root where { $root.d };
    has App::insulcalc::Plan @!plans;
    has App::insulcalc::Scenario @!scenarios;

    method run {
        say "Root = $!root"
    }
}

Gives me

===SORRY!=== Error while compiling /home/autarch/projects/App-insucalc/lib/App/insucalc.pm6
Variable '$root' is not declared. Did you mean '&roots'?
at /home/autarch/projects/App-insucalc/lib/App/insucalc.pm6:15
------>     has Dir $!root where { ⏏$root.d };
  from ./bin/insulcalc:6