package SomeThing;

        use overload
            '+' => \&myadd,
            '-' => \&mysub;
            # etc
        ...

        package main;
        $a = new SomeThing 57;
        $b=5+$a;
        ...
        if (overload::Overloaded $b) {...}
        ...
        $strval = overload::StrVal $b;