/usr/share/perl5/Plack/Middleware/ is in libplack-middleware-debug-perl 0.16+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/perl5/Plack/Middleware/Debug/
/usr/share/perl5/Plack/Middleware/Debug.pm
/usr/share/perl5/Plack/Middleware/Debug/Base.pm
/usr/share/perl5/Plack/Middleware/Debug/CatalystLog.pm
/usr/share/perl5/Plack/Middleware/Debug/DBITrace.pm
/usr/share/perl5/Plack/Middleware/Debug/Environment.pm
/usr/share/perl5/Plack/Middleware/Debug/Memory.pm
/usr/share/perl5/Plack/Middleware/Debug/ModuleVersions.pm
/usr/share/perl5/Plack/Middleware/Debug/Panel.pm
/usr/share/perl5/Plack/Middleware/Debug/Parameters.pm
/usr/share/perl5/Plack/Middleware/Debug/PerlConfig.pm
/usr/share/perl5/Plack/Middleware/Debug/Response.pm
/usr/share/perl5/Plack/Middleware/Debug/Session.pm
/usr/share/perl5/Plack/Middleware/Debug/Timer.pm
/usr/share/perl5/Plack/Middleware/Debug/TrackObjects.pm