gistfile1.txt

C:\Consulting\rakudo>type test.p6
class A {
    method foo($c) {
        $c()
    }
}

sub bar() {
    A.foo({
        'lol'.subst(/l/, { wtf() });
    });
}

bar();

C:\Consulting\rakudo>perl6 test.p6
Could not find sub &wtf
in <anon> at line 9:test.p6
in 'Cool::subst' at line 1838:CORE.setting
in <anon> at line 9:test.p6
in 'A::foo' at line 3:test.p6
in 'bar' at line 8:test.p6
in main program body at line 13:test.p6