> .for file in ${MYFILES}
> 	cp ${file} dir/file{$n}
> .endfor

n := 1
.for file in $(MYFILES)
	cp $(file) dir/file$(n)
	n != echo $(($(n)+1))   # or != expr $(n) + 1
.endfor

I don't know of any way to do the arithmetic itself within make.  For
general arithmetic, it's probably possible, but I suspect only with the
help of an include file which implements recursion through re-including
itself.  However, incrementing is a special case:

n := 1
.for file in $(MYFILES)
	cp $(file) dir/file$(n)
	n1 := $(n:C/\(.*\)\(.\)\(9*\)/\1/)
	n2 := $(n:C/\(.*\)\(.\)\(9*\)/\2/)
	n3 := $(n:C/\(.*\)\(.\)\(9*\)/\3/)
	n := $(n1)$(n2:S/9/10/:S/8/9/:S/7/8/:S/6/7/:S/5/6/:S/4/5/:S/3/4/:S/2/3:S/1/2/:S/0/1/)$(n3:S/9/0/g)
.endfor

The three regex lines can probably be done with only one regex line,
producing a string containing delimiters, picking apart the result
separately.

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