perl - perl v24 中的 ${^MATCH} 和/p 修饰符

Question

perlre说:

p

Preserve the string matched such that ${^PREMATCH} , ${^MATCH} , and ${^POSTMATCH} are available for use after matching.

In Perl 5.20 and higher this is ignored. Due to a new copy-on-write mechanism, ${^PREMATCH} , ${^MATCH} , and ${^POSTMATCH} will be available after the match regardless of the modifier.

还有 perlvar

${^MATCH} This is similar to $& ($MATCH ) except that it does not incur the performance penalty associated with that variable.

In Perl v5.18 and earlier, it is only guaranteed to return a defined value when the pattern was compiled or executed with the /p modifier. In Perl v5.20, the /p modifier does nothing, so ${^MATCH} does the same thing as $MATCH .

测试:

echo 'Lorem ipsum dolor sit ut dicta qui dolores.' |\
 perl -nE 'say ${^MATCH} while m/dolor/g'

输出:两个空行(2x \n)

但是:

echo 'Lorem ipsum dolor sit ut dicta qui dolores.' |\
 perl -nE 'say ${^MATCH} while m/dolor/gp'

输出:

dolor
dolor

我的perl:

$ perl -v

This is perl 5, version 24, subversion 0 (v5.24.0) built for darwin-2level
(with 1 registered patch, see perl -V for more detail)

所以在 5.24.0 /p还需要修改器吗？或者我错过了什么？

Answer 1

代码的行为与记录在案的行为之间确实存在差异。提交错误报告作为票 RT#131087 .

作为解决方法，您可以使用 $& ( $MATCH )。