Programming :: Makefile Index Of List Element?

So I have been trying for 8 hours to try to get the index of an element from a list in a Makefile. The problem is that after I get the index using all the methods I have tried, the index cant be used in the "word" function:

for instance:
$(OUTPUT2) : INDEX = $(shell echo $(OUTPUT2) | sed -r -e "s/[ ]+/
/g" | grep -n $@ | sed 's/^([0-9]*):.*/1/')

will create a variable INDEX defined specifically for each member of OUTPUT2, so that each output knows its index. Unfortunately, when I pass this $(INDEX) into word, it doesn't work:

$(OUTPUT2) : $(word $(INDEX), $(INPUT1)) $(word $(INDEX), $(INPUT2))
echo $(INAME) $(TMPBASE) $@
and I get the error:
Makefile:16: *** non-numeric first argument to `word' function: 'num'. Stop.

I feel like if I could just convert a string to a Makefile acceptable number this would just work....