sub test {
    use attrs qw(locked method);
    ...
}
@a = attrs::get(\test);

You should use a form like the following instead:

sub test : locked method { }

You can read more about attributes in the next section.

The valid attributes are:

locked

Meaningful only when the subroutine or method will be called by multiple threads. When set on a subroutine that also has the method attribute set, invoking that subroutine implicitly locks its first argument before execution. On a non-method subroutine, a lock is taken on the subroutine itself before execution. The lock semantics are identical to one taken explicitly with the lock operator immediately after entering the subroutine.

method

The invoking subroutine is a method.

8.3. attributes		8.5. AutoLoader