/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/ is in libpetsc-complex-3.7.7-dev 3.7.7+dfsg1-2build5.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenFile/
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenFile/PetscOpenFile.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenFile/close.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenFile/read.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenFile/write.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenSocket/
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenSocket/PetscOpenSocket.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenSocket/close.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenSocket/read.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/@PetscOpenSocket/write.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/PetscBagRead.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/PetscBinaryRead.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/PetscBinaryWrite.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/PetscReadBinaryMatlab.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/PetscReadBinaryTrajectory.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/UFgetPetscMat.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/generatePetscTestFiles.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/laplacian.m
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/laplacianlicense.txt
/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-complex/share/petsc/matlab/launch.m