/usr/share/perl5/Plack/Middleware/ is in libplack-perl 1.0033-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/perl5/Plack/Middleware/AccessLog/
/usr/share/perl5/Plack/Middleware/AccessLog.pm
/usr/share/perl5/Plack/Middleware/AccessLog/Timed.pm
/usr/share/perl5/Plack/Middleware/Auth/
/usr/share/perl5/Plack/Middleware/Auth/Basic.pm
/usr/share/perl5/Plack/Middleware/BufferedStreaming.pm
/usr/share/perl5/Plack/Middleware/Chunked.pm
/usr/share/perl5/Plack/Middleware/Conditional.pm
/usr/share/perl5/Plack/Middleware/ConditionalGET.pm
/usr/share/perl5/Plack/Middleware/ContentLength.pm
/usr/share/perl5/Plack/Middleware/ContentMD5.pm
/usr/share/perl5/Plack/Middleware/ErrorDocument.pm
/usr/share/perl5/Plack/Middleware/HTTPExceptions.pm
/usr/share/perl5/Plack/Middleware/Head.pm
/usr/share/perl5/Plack/Middleware/IIS6ScriptNameFix.pm
/usr/share/perl5/Plack/Middleware/IIS7KeepAliveFix.pm
/usr/share/perl5/Plack/Middleware/JSONP.pm
/usr/share/perl5/Plack/Middleware/LighttpdScriptNameFix.pm
/usr/share/perl5/Plack/Middleware/Lint.pm
/usr/share/perl5/Plack/Middleware/Log4perl.pm
/usr/share/perl5/Plack/Middleware/LogDispatch.pm
/usr/share/perl5/Plack/Middleware/NullLogger.pm
/usr/share/perl5/Plack/Middleware/RearrangeHeaders.pm
/usr/share/perl5/Plack/Middleware/Recursive.pm
/usr/share/perl5/Plack/Middleware/Refresh.pm
/usr/share/perl5/Plack/Middleware/Runtime.pm
/usr/share/perl5/Plack/Middleware/SimpleContentFilter.pm
/usr/share/perl5/Plack/Middleware/SimpleLogger.pm
/usr/share/perl5/Plack/Middleware/StackTrace.pm
/usr/share/perl5/Plack/Middleware/Static.pm
/usr/share/perl5/Plack/Middleware/XFramework.pm
/usr/share/perl5/Plack/Middleware/XSendfile.pm