/usr/include/d/std/internal/ is in libphobos2-ldc-dev 1:0.17.1-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/d/std/internal/cstring.d
/usr/include/d/std/internal/digest/
/usr/include/d/std/internal/digest/sha_SSSE3.d
/usr/include/d/std/internal/math/
/usr/include/d/std/internal/math/biguintcore.d
/usr/include/d/std/internal/math/biguintnoasm.d
/usr/include/d/std/internal/math/biguintx86.d
/usr/include/d/std/internal/math/errorfunction.d
/usr/include/d/std/internal/math/gammafunction.d
/usr/include/d/std/internal/processinit.d
/usr/include/d/std/internal/scopebuffer.d
/usr/include/d/std/internal/test/
/usr/include/d/std/internal/test/dummyrange.d
/usr/include/d/std/internal/unicode_comp.d
/usr/include/d/std/internal/unicode_decomp.d
/usr/include/d/std/internal/unicode_grapheme.d
/usr/include/d/std/internal/unicode_norm.d
/usr/include/d/std/internal/unicode_tables.d
/usr/include/d/std/internal/windows/
/usr/include/d/std/internal/windows/advapi32.d