/usr/include/root/Reflex/internal/ is in libroot-core-dev 5.34.19+dfsg-1.2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/root/Reflex/internal/BuilderContainer.h
/usr/include/root/Reflex/internal/InternalTools.h
/usr/include/root/Reflex/internal/LiteralString.h
/usr/include/root/Reflex/internal/MemberBase.h
/usr/include/root/Reflex/internal/MemberTemplateImpl.h
/usr/include/root/Reflex/internal/MemberTemplateName.h
/usr/include/root/Reflex/internal/OwnedMember.h
/usr/include/root/Reflex/internal/OwnedMemberTemplate.h
/usr/include/root/Reflex/internal/OwnedPropertyList.h
/usr/include/root/Reflex/internal/PropertyListImpl.h
/usr/include/root/Reflex/internal/ScopeBase.h
/usr/include/root/Reflex/internal/ScopeName.h
/usr/include/root/Reflex/internal/TypeBase.h
/usr/include/root/Reflex/internal/TypeName.h
/usr/include/root/Reflex/internal/TypeTemplateImpl.h
/usr/include/root/Reflex/internal/TypeTemplateName.h