make(1): is this a bug or PEBKAC?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

I'm trying to work on 9.1, for work.  Of course, one of the first
things I tried to do was install various of my tools.

make(1) appears to be misbehaving.  But I'm not sure enough it isn't
PEBKAC to just file a PR.

Specifically, I run my "bootstrap the tools" script and everything goes
normally until it tries to build a particular program, at which point

make: Unclosed substitution for  (; missing)
make: Unclosed substitution for  (; missing)
make: "/home/mouse/..local/lib/make/local-prog" line 115: Need an operator
make: Unclosed substitution for  (; missing)
make: Unclosed substitution for  (; missing)
make: "/home/mouse/..local/lib/make/local-prog" line 121: Need an operator
make: Unclosed substitution for  (; missing)
make: "/home/mouse/..local/lib/make/local-prog" line 125: Need an operator
make: Fatal errors encountered -- cannot continue

There are exactly two spaces between "for" and "(" on the "Unclosed
substitution" lines (verified with hexdump -C).  The Makefile in
question is

CC_ADD = -g
BUILDBINS = ccwrapper
OBJ_ccwrapper = ccwrapper.o
INSTALLMAN = ccwrapper.1

.MAIN: ccwrapper ccwrapper.cat1

.include <local-prog>

and make is being run as...well, to let ktrace -t aceinsu tell it:

  3662      1 make     NAMI  "/usr/bin/make"
  3662      1 make     NAMI  "/usr/libexec/ld.elf_so"
  3662      1 make     ARG   "/usr/bin/make"
  3662      1 make     ARG   "-m"
  3662      1 make     ARG   "/home/mouse/..local/lib/make"
  3662      1 make     ARG   "-m"
  3662      1 make     ARG   "/usr/share/mk"

(local-prog is the only thing in /home/.mouse/..local/lib/make.)

The relevant part of local-prog is (line numbers added, of course - the
whole file is on ftp.rodents-montreal.org in
/pub/mouse/local/src/makefiles/makefiles-20230221/local-prog in case
anyone wants the whole thing):

   109	.PHONY: install_dirs_MAN
   110	.for x in $(INSTALLMAN)
   111	install_files:: $(x:C;^(.*)\.([0-9].*)$$;$(INSTMANDIR)/cat\2/\1.0;)
   112	install_dirs:: install_dirs_MAN
   113	$(x:C;^(.*)\.([0-9].*)$$;$(INSTMANDIR)/cat\2/\1.0;):		\
   114			$(x:C;^.*\.([0-9].*)$$;$(INSTMANDIR)/cat\1;)	\
   115			$(x:C;\.([0-9].*)$$;.cat\1;)
   116		cp $(x:C;\.([0-9].*)$$;.cat\1;) $(.TARGET)
   117	CLEANFILES_ += $(x:C;\.([0-9].*)$$;.cat\1;)
   118	.if !exists($(x:C;^.*\.([0-9].*)$$;$(INSTMANDIR)/cat\1;)) && \
   119	    !target($(x:C;^.*\.([0-9].*)$$;$(INSTMANDIR)/cat\1;))
   120	install_dirs_MAN:: $(x:C;^.*\.([0-9].*)$$;$(INSTMANDIR)/cat\1;)
   121	$(x:C;^.*\.([0-9].*)$$;$(INSTMANDIR)/cat\1;):
   122		mkdir -p $(.TARGET)
   123	.endif
   124	.if !target($(x:C;\.([0-9].*)$$;.cat\1;))
   125	$(x:C;\.([0-9].*)$$;.cat\1;): $(x)
   126		nroff -mandoc $(.ALLSRC) > $(.TARGET) || (rm -f $(.TARGET); false)
   127	.endif
   128	.endfor

The same code works with 5.2's make (which, of course, says only
moderately little for its correctness...).

So, I'm wondering, is this a bug in 9.1's make, or am I doing something
wrong here?

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