知道为什么 CPAN 被锁定在循环依赖中，尽管我只发出 get 吗？
这只发生在我从全新的 Perl 安装（或删除 CPAN/源目录）开始时：
cpan[1]> get Devel::Declare
CPAN: CPAN::SQLite loaded ok (v0.202)
CPAN: LWP::UserAgent loaded ok (v6.04)
CPAN: Time::HiRes loaded ok (v1.9725)
Fetching with LWP:
http://cpan.yimg.com/authors/01mailrc.txt.gz
CPAN: YAML::XS loaded ok (v0.38)
Fetching with LWP:
http://cpan.yimg.com/modules/02packages.details.txt.gz
Fetching with LWP:
http://cpan.yimg.com/modules/03modlist.data.gz
Database was generated on Sun, 12 Aug 2012 19:51:28 GMT
Running get for module 'Devel::Declare'
CPAN: CPAN::Kwalify loaded ok (v5.50)
Fetching with LWP:
http://cpan.yimg.com/authors/id/Z/ZE/ZEFRAM/Devel-Declare-0.006011.tar.gz
CPAN: Digest::SHA loaded ok (v5.71)
Fetching with LWP:
http://cpan.yimg.com/authors/id/Z/ZE/ZEFRAM/CHECKSUMS
CPAN: Compress::Zlib loaded ok (v2.049)
Checksum for C:\CPANTesters\cpan\sources\authors\id\Z\ZE\ZEFRAM\Devel-Declare-0.
006011.tar.gz ok
CPAN: Archive::Tar loaded ok (v1.88)
Devel-Declare-0.006011/
Devel-Declare-0.006011/META.yml
...
Devel-Declare-0.006011/t/statement.t
Devel-Declare-0.006011/t/early1_x.pm
Devel-Declare-0.006011/t/combi.t
CPAN: File::Temp loaded ok (v0.22)
CPAN: Parse::CPAN::Meta loaded ok (v1.4402)
CPAN: CPAN::Meta loaded ok (v2.120630)
CPAN: Module::CoreList loaded ok (v2.66)
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
Fetching with LWP:
http://cpan.yimg.com/authors/id/Z/ZE/ZEFRAM/B-Hooks-OP-Check-0.19.tar.gz
Checksum for C:\CPANTesters\cpan\sources\authors\id\Z\ZE\ZEFRAM\B-Hooks-OP-Check
-0.19.tar.gz ok
B-Hooks-OP-Check-0.19/
B-Hooks-OP-Check-0.19/META.yml
...
B-Hooks-OP-Check-0.19/t/
B-Hooks-OP-Check-0.19/t/use.t
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
---- Unsatisfied dependencies detected during ----
---- ZEFRAM/Devel-Declare-0.006011.tar.gz ----
B::Hooks::OP::Check [build_requires]
Running get for module 'B::Hooks::OP::Check'
Caught SIGINT, trying to continue
该命令由 Ctrl-C 终止
Perl 是 Windows 7 64 位上的 ActiveState Perl v5.16.0
CPAN.pm 是 1.9800