multi sub do-a-b-c (UsefulClass $cc) {
    $cc.do-a;
    $cc.do-b;
    $cc.do-c;
}

multi sub do-a-b-c (Int $a) { do-a-b-c UsefulClass.new($a) }
multi sub do-a-b-c (Str $a) { do-a-b-c UsefulClass.new($a) }

multi sub do-a-c (UsefulClass $cc) {
    $cc.do-a;
    $cc.do-c;
}

multi sub do-a-c (Int $a) { do-a-c UsefulClass.new($a) }
multi sub do-a-c (Str $a) { do-a-c UsefulClass.new($a) }