perl - (+) 裸字和移位运算符有什么用？

Question

我正在学习中级 perl。现在我正在研究类的对象引用。因为他们提供了一个包

{
    package Barn;

    sub new { bless [], shift }

    sub add { push @{ +shift }, shift }

    sub contents { @{ +shift } }

    sub DESTROY {
        my $self = shift;
        print "$self is being destroyed...\n";
        for ( $self->contents ) {
            print ' ', $_->name, " goes homeless.\n";
        }
    }
}

in this I can't understand the work of plus sign with shift operator. In text they said ,the plus sign is like bareword it would be interpreted as a soft reference: @{"shift"}

你能清楚地解释它使用加号和移位运算符的工作吗？

Answer 1

没有加号，@{shift}与数组 @shift 相同不调用 shift运营商。添加加号强制 shift要作为表达式求值，所以 shift运算符被称为

我更愿意看到@{ shift() }
方法通常被编写为将第一个参数提取到 $self ， 像这样

sub new {
    my $class = shift;
    bless [ ], $class;
}

sub add {
    my $self = shift;
    push @$self, shift;
}

sub contents {
    my $self = shift;
    return @$self;
}