Line 61 and 62 of regex/Makefile.in are both supposed to be commented out.   These two lines appear as follows (that should be whitespace at the beginning of each line):

	#cmp -s regex.tmp regex.h 2>/dev/null || cp regex.tmp regex.h
	#rm -f regex.tmp

 It appears that Digital Unix 'make' does not like whitespace before comments though.  Thus when compiling regex I get errors such as the following:

sh ./mkh  -i _REGEX_H_ regex2.h regcomp.c regerror.c regexec.c regfree.c>regex.h
#cmp -s regex.tmp regex.h 2>/dev/null || cp regex.tmp regex.h
#rm -f regex.tmp
#rm: No such file or directory
*** Exit 1
Stop.

The simple way to fix this is to remove the whitespace before the beginning of the comments.