Perl 字符串是不可变的吗? [英] Are Perl strings immutable?

问题描述

当我对字符串进行连接时，幕后发生了什么?

What's happening behind the scenes when I do a concatenation on a string?

my $short = 'short';
$short .= 'cake';

Perl 是否有效地创建了一个新字符串，然后为其分配了正确的变量引用，还是 Perl 字符串本质上总是可变的?

Is Perl effectively creating a new string, then assigning it the correct variable reference, or are Perl strings always mutable by nature?

提出这个问题的动机来自我与一位同事的讨论，他说脚本语言可以使用不可变字符串.

The motivation for this question came from a discussion I had with a colleague, who said that scripting languages can utilize immutable strings.

推荐答案

Perl 字符串是可变的.如果需要，Perl 会自动创建新的缓冲区.

Perl strings are mutable. Perl automatically creates new buffers, if required.

use Devel::Peek;
my $short = 'short';

Dump($short);
Dump($short .= 'cake');
Dump($short = "");

SV = PV(0x28403038) at 0x284766f4
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x28459078 "short"\0
  CUR = 5
  LEN = 8
SV = PV(0x28403038) at 0x284766f4
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x28458120 "shortcake"\0
  CUR = 9
  LEN = 12
SV = PV(0x28403038) at 0x284766f4
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x28458120 ""\0
  CUR = 0
  LEN = 12

注意在第三种情况下没有分配新的缓冲区.

Note that no new buffer is allocated in the third case.

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