sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)

brad@freebsd-vmware-amd64:~/tmp/zlib-ng/build $ ../configure
Checking for compiler... cc
Checking for Symbol versioning... Yes.
Checking for shared library support... Building shared library libz-ng.so.2.3.0 with cc.
Checking for -Werror=unguarded-availability... No.
Checking for -Werror=unguarded-availability-new... No.
Checking for -Werror=unused-command-line-argument... No.
Checking for version script support... No.
Checking for off64_t... Yes.
Checking for fseeko... Yes.
Checking for GNU style __cpuid... Yes.
Checking for MS style __cpuid... No.
Checking for strerror... Yes.
Checking for getauxval() or elf_aux_info() in sys/auxv.h... Yes.
Checking for unistd.h... Yes.
Checking for linux/auxvec.h... No.
Checking for ptrdiff_t... Yes.
Checking for ANSI C compliant compiler...  Yes.
Checking for -fno-semantic-interposition... No.
Checking for attribute(aligned) ... Yes.
Checking for __builtin_assume_aligned() ... Yes.
Checking for __builtin_ctz ... Yes.
Checking for __builtin_ctzll ... Yes.
Checking for XSAVE intrinsics ... Yes.
Checking for SSE2 intrinsics ... Yes.
Checking for SSSE3 intrinsics ... Yes.
Checking for SSE4.1 intrinsics ... Yes.
Checking for SSE4.2 intrinsics ... Yes.
Checking for PCLMULQDQ intrinsics ... Yes.
Checking for AVX2 intrinsics ... Yes.
Checking for AVX512 intrinsics ... Yes.
Check whether -mtune=cascadelake works ... Yes.
Checking for AVX512VNNI intrinsics ... Yes.
Checking for VPCLMULQDQ intrinsics ... Yes.
Uname: FreeBSD 14.3-RELEASE
ARCH: amd64
Using arch directory: arch/x86
Architecture-specific static object files: x86_features.o chunkset_sse2.o chorba_sse2.o compare256_sse2.o slide_hash_sse2.o adler32_ssse3.o chunkset_ssse3.o chorba_sse41.o adler32_sse42.o crc32_pclmulqdq.o slide_hash_avx2.o chunkset_avx2.o compare256_avx2.o adler32_avx2.o adler32_avx512.o chunkset_avx512.o compare256_avx512.o adler32_avx512_vnni.o crc32_vpclmulqdq.o
Architecture-specific shared object files: x86_features.lo chunkset_sse2.lo chorba_sse2.lo compare256_sse2.lo slide_hash_sse2.lo adler32_ssse3.lo chunkset_ssse3.lo chorba_sse41.lo adler32_sse42.lo crc32_pclmulqdq.lo slide_hash_avx2.lo chunkset_avx2.lo compare256_avx2.lo adler32_avx2.lo adler32_avx512.lo chunkset_avx512.lo compare256_avx512.lo adler32_avx512_vnni.lo crc32_vpclmulqdq.lo
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
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sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
sed: 1: "s/# *\include *"\(.*\.h ...": RE error: trailing backslash (\)
brad@freebsd-vmware-amd64:~/tmp/zlib-ng/build $