为什么 $a 会变成一个数组引用?我没有强迫它.
Why does $a become an arrayref? I'm not pushing anything to it.
perl -MData::Dumper -e 'use strict; 1 for @$a; print Dumper $a' $VAR1 = []; 推荐答案这是因为 for 循环将 @$a 的内容视为左值——你可以赋值给.请记住,for 将数组的内容别名为 $_.看起来,在 @$a 中寻找可别名内容的行为足以导致自动激活,即使没有要别名的内容也是如此.
It is because the for loop treats contents of @$a as lvalues--something that you can assign to. Remember that for aliases the contents of the array to $_. It appears that the act of looking for aliasable contents in @$a, is sufficient to cause autovivification, even when there are no contents to alias.
这种混叠效果也是一致的.以下内容也会导致自动激活:
This effect of aliasing is consistent, too. The following also lead to autovivification:
- map {stuff} @$a;
- grep {stuff} @$a;
- a_subroutine(@$a);
如果你想管理自动激活,你可以使用同名pragma来实现词法控制.
If you want to manage autovivification, you can use the eponymous pragma to effect lexical controls.
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为什么在这种情况下 Perl 会自动激活?
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