regex - 为什么我不能连接在 qr 下编译和运行时评估的模式？

Question

为什么这颗炸弹

perl -e 'print qr{$_(??{$_})}'

虽然这两者是分开工作的:

perl -e 'print qr{$_}'
perl -e 'print qr{(??{$_})}'

错误信息是

Eval-group not allowed at runtime, use re 'eval' in regex m/(??{$_})/ at -e line 1.

真的，我应该升级 Perl 吗？我有5.14.4。

Answer 1

这是 5.18.0 中修复的错误和5.17.1。

The implementation of code blocks in regular expressions, such as (?{}) and (??{}), has been heavily reworked to eliminate a whole slew of bugs. The main user-visible changes are:

• Code blocks within patterns are now parsed in the same pass as the surrounding code;

• Lexical variables are now sane as regards scope, recursion and closure behavior.