There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.

PRBRENAN / Silicon-Chip-Btree-20231112 / CHANGES 
2023-10-25 Now available on GitHub at: https://github.com/philiprbrenan/SiliconChipBtree
           Please create a pull request from a cloned copy.
2020-10-30 Now available on GitHub at: https://github.com/philiprbrenan/SiliconChipBtree
           Please create a pull request from a cloned copy.