/usr/include/libMUSCLE-3.7/libMUSCLE/ is in libmuscle-3.7-dev 3.7+4565-2.
This file is owned by root:root, with mode 0o755.
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/usr/include/libMUSCLE-3.7/libMUSCLE/alpha.h
/usr/include/libMUSCLE-3.7/libMUSCLE/clust.h
/usr/include/libMUSCLE-3.7/libMUSCLE/cluster.h
/usr/include/libMUSCLE-3.7/libMUSCLE/clustset.h
/usr/include/libMUSCLE-3.7/libMUSCLE/clustsetdf.h
/usr/include/libMUSCLE-3.7/libMUSCLE/clustsetmsa.h
/usr/include/libMUSCLE-3.7/libMUSCLE/diaglist.h
/usr/include/libMUSCLE-3.7/libMUSCLE/distcalc.h
/usr/include/libMUSCLE-3.7/libMUSCLE/distfunc.h
/usr/include/libMUSCLE-3.7/libMUSCLE/dpregionlist.h
/usr/include/libMUSCLE-3.7/libMUSCLE/dpreglist.h
/usr/include/libMUSCLE-3.7/libMUSCLE/edgelist.h
/usr/include/libMUSCLE-3.7/libMUSCLE/enumopts.h
/usr/include/libMUSCLE-3.7/libMUSCLE/enums.h
/usr/include/libMUSCLE-3.7/libMUSCLE/estring.h
/usr/include/libMUSCLE-3.7/libMUSCLE/gapscoredimer.h
/usr/include/libMUSCLE-3.7/libMUSCLE/gonnet.h
/usr/include/libMUSCLE-3.7/libMUSCLE/intmath.h
/usr/include/libMUSCLE-3.7/libMUSCLE/msa.h
/usr/include/libMUSCLE-3.7/libMUSCLE/msadist.h
/usr/include/libMUSCLE-3.7/libMUSCLE/muscle.h
/usr/include/libMUSCLE-3.7/libMUSCLE/objscore.h
/usr/include/libMUSCLE-3.7/libMUSCLE/params.h
/usr/include/libMUSCLE-3.7/libMUSCLE/profile.h
/usr/include/libMUSCLE-3.7/libMUSCLE/pwpath.h
/usr/include/libMUSCLE-3.7/libMUSCLE/refine.h
/usr/include/libMUSCLE-3.7/libMUSCLE/scorehistory.h
/usr/include/libMUSCLE-3.7/libMUSCLE/seq.h
/usr/include/libMUSCLE-3.7/libMUSCLE/seqvect.h
/usr/include/libMUSCLE-3.7/libMUSCLE/textfile.h
/usr/include/libMUSCLE-3.7/libMUSCLE/threadstorage.h
/usr/include/libMUSCLE-3.7/libMUSCLE/timing.h
/usr/include/libMUSCLE-3.7/libMUSCLE/tree.h
/usr/include/libMUSCLE-3.7/libMUSCLE/types.h
/usr/include/libMUSCLE-3.7/libMUSCLE/unixio.h