adding a shell function

[Jeff Fulmer]

Forgive me if this is an obvious question, but I've been unable to
find the answer. I'd like to add a sh function to configure. 

I figured I could add something like this to acinclude.m4:

foo(){
  echo $1 | /usr/bin/sed 's/[A-Za-z]$/&\//g'
} 

then in configure.in I could add something like this:

HAHA=`foo "/home/jeff"`
AC_SUBST(HAHA)

autoconf never complains about this, but HAHA is never defined. Could
anyone tell me what I'm missing?

TIA,
Jeff

-- 
#include <stdio.h>
int main(){int a[]={74,117,115,116,32,97,110,111,116,104,101,114,32, \
67,32,104,97,99,107,101,114,10,0}; int *b=a;while(*b>0)putchar(*b++);}