/usr/lib/perl5/Mouse/ is in libmouse-perl 2.1.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/perl5/Mouse/Exporter.pm
/usr/lib/perl5/Mouse/Meta/
/usr/lib/perl5/Mouse/Meta/Attribute.pm
/usr/lib/perl5/Mouse/Meta/Class.pm
/usr/lib/perl5/Mouse/Meta/Method/
/usr/lib/perl5/Mouse/Meta/Method.pm
/usr/lib/perl5/Mouse/Meta/Method/Accessor.pm
/usr/lib/perl5/Mouse/Meta/Method/Constructor.pm
/usr/lib/perl5/Mouse/Meta/Method/Delegation.pm
/usr/lib/perl5/Mouse/Meta/Method/Destructor.pm
/usr/lib/perl5/Mouse/Meta/Module.pm
/usr/lib/perl5/Mouse/Meta/Role/
/usr/lib/perl5/Mouse/Meta/Role.pm
/usr/lib/perl5/Mouse/Meta/Role/Application.pm
/usr/lib/perl5/Mouse/Meta/Role/Composite.pm
/usr/lib/perl5/Mouse/Meta/Role/Method.pm
/usr/lib/perl5/Mouse/Meta/TypeConstraint.pm
/usr/lib/perl5/Mouse/Object.pm
/usr/lib/perl5/Mouse/PurePerl.pm
/usr/lib/perl5/Mouse/Role.pm
/usr/lib/perl5/Mouse/Spec.pm
/usr/lib/perl5/Mouse/Tiny.pm
/usr/lib/perl5/Mouse/Tiny.pod
/usr/lib/perl5/Mouse/TypeRegistry.pm
/usr/lib/perl5/Mouse/Util/
/usr/lib/perl5/Mouse/Util.pm
/usr/lib/perl5/Mouse/Util/MetaRole.pm
/usr/lib/perl5/Mouse/Util/TypeConstraints.pm
/usr/lib/perl5/Mouse/XS.pod