/usr/include/regina-normal/packet/ is in regina-normal-dev 4.96-2.1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/regina-normal/packet/ncontainer.h
/usr/include/regina-normal/packet/npacket.h
/usr/include/regina-normal/packet/npacketlistener.h
/usr/include/regina-normal/packet/npdf.h
/usr/include/regina-normal/packet/nscript.h
/usr/include/regina-normal/packet/ntext.h
/usr/include/regina-normal/packet/nxmlpacketreader.h
/usr/include/regina-normal/packet/nxmlpacketreaders.h
/usr/include/regina-normal/packet/nxmltreeresolver.h
/usr/include/regina-normal/packet/packetregistry-impl.h
/usr/include/regina-normal/packet/packetregistry.h
/usr/include/regina-normal/packet/packettype.h