Fix technical issues and improve consistency

- Correct README chapter links to match actual filenames
- Fix Modern::Perl version from invalid '2023' to valid '2018'
- Ensure all code examples use proper Perl syntax and best practices
- Maintain consistency across all chapters

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

16-testing-and-debugging.md

@@ -604,7 +604,7 @@ jobs:
 
 ```perl
 #!/usr/bin/env perl
-use Modern::Perl '2023';
+use Modern::Perl '2018';
 use TAP::Harness;
 use File::Find;
 use Getopt::Long;
@@ -655,7 +655,7 @@ exit($aggregator->all_passed() ? 0 : 1);
 ```perl
 #!/usr/bin/env perl
 # t/web_scraper.t
-use Modern::Perl '2023';
+use Modern::Perl '2018';
 use Test::More;
 use Test::MockModule;
 use Test::Deep;