从ysth的评论：

The warning happens when the sub has the same name as a builtin and it is called without & and not as a method call; perl uses the builtin instead but gives a warning. The :method quiets the warning because it clearly indicates the sub was never intended to be called as a non-method anyway.

更新

调用foo时,此代码只调用方法栏：

sub foo : method {  ## Mark function as method
    shift->bar(@_)  ## Pass all parameters to bar method of same object
}

更多细节：

>：method – 表示引用的子例程是一个方法.如此标记的子程序不会触发“不明确的调用解析为CORE ::％s”警告.
> shift – 从@_获取第一个参数,这将是$self
> – > bar(@_) – 使用所有其他参数调用相同的类方法栏

你可以这样读：

sub foo : method {
    my ($self) = shift @_; 
    return $self->bar(@_);
}