为什么smartmatch在比较应该不同的数组切片时会返回true？

Question

以下脚本智能匹配两个数组的切片.一开始,两个阵列都是一样的,我得到了合理的结果.然后我改变其中一个数组并智能匹配两个新切片,但它仍然说切片是相同的.但是,当我将切片复制到数组中时,对数组进行智能匹配表明它们确实不同.

剧本:

#!/usr/bin/perl
use warnings;
use strict;
use diagnostics;

my @x = qw (one two);
my @y = qw (one two);
my @x_s;
my @y_s;

print "Before change: values are the same:\n";
@x_s = @x[0,1];
@y_s = @y[0,1];
print "\@x_s: @x_s\n";
print +(@x[0,1] ~~ @y[0,1]) ? "equal\n" : "not equal\n";
print +(@x_s ~~ @y_s) ? "equal\n" : "not equal\n";

$x[0]='three';

print "After change: values should be different:\n";
@x_s = @x[0,1];
@y_s = @y[0,1];
print "\@x_s: @x_s\n";
print +(@x[0,1] ~~ @y[0,1]) ? "equal\n" : "not equal\n";
print +(@x_s ~~ @y_s) ? "equal\n" : "not equal\n";

输出:

Before change: values are the same:
@x_s: one two
equal
equal
After change: values should be different:
@x_s: three two
equal
not equal

我正在使用Perl 5.10.1,这对于数组切片和散列切片都会发生.为什么会这样？

Answer 1

看起来智能匹配在带有切片的标量上下文中工作.

请考虑以下代码:

你的情况:

#!/usr/bin/perl

my @foo = (1,2);
my @bar = (3,4);
print @foo[1,2] ~~ @bar[1,2] ? "Equal\n" : "Not equal\n";

这可能就是你所需要的:

#!/usr/bin/perl

my @foo = (1,2);
my @bar = (3,4);
print [ @foo[1,2] ] ~~ [ @bar[1,2] ] ? "Equal\n" : "Not equal\n";