perl - %^H 在 Perl 中有什么用？

Question

有谁知道这个全局变量是做什么的？

由于特殊字符，我无法通过 google 找到任何信息。

更新

[root@dev-test v2]$ perldoc -v '%^H'
Ending switch processing.  Args are [%^H] with 0 errors.
/usr/bin/perldoc => Pod::Perldoc v3.14

Formatter class Pod::Perldoc::ToMan successfully loaded!
Will format with the class Pod::Perldoc::ToMan
Searching for %^H
Looking for %^H in /usr/bin /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.7/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.6/x86_64-linux-thread-multi /usr/lib64/perl5/site_perl/5.8.5/x86_64-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl/5.8.7 /usr/lib/perl5/site_perl/5.8.6 /usr/lib/perl5/site_perl/5.8.5 /usr/lib/perl5/site_perl /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.7/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.6/x86_64-linux-thread-multi /usr/lib64/perl5/vendor_perl/5.8.5/x86_64-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl/5.8.7 /usr/lib/perl5/vendor_perl/5.8.6 /usr/lib/perl5/vendor_perl/5.8.5 /usr/lib/perl5/vendor_perl /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi /usr/lib/perl5/5.8.8 . /usr/kerberos/bin /usr/lib64/ccache /usr/local/bin /bin /usr/bin
No documentation found for "%^H".

Answer 1

来自 http://perldoc.perl.org/perlvar.html :

•%^H
The %^H hash provides the same scoping semantic as $^H. This makes it useful for implementation of lexically scoped pragmas. See perlpragma.

This variable was added in Perl 5.6.