Something

  for element in $INCINTL; do
    haveit=
    for x in $CPPFLAGS; do

  acl_save_prefix="$prefix"
  prefix="$acl_final_prefix"
  acl_save_exec_prefix="$exec_prefix"
  exec_prefix="$acl_final_exec_prefix"
  eval x=\"$x\"
  exec_prefix="$acl_save_exec_prefix"
  prefix="$acl_save_prefix"

      if test "X$x" = "X$element"; then
        haveit=yes
        break
      fi
    done
    if test -z "$haveit"; then
      CPPFLAGS="${CPPFLAGS}${CPPFLAGS:+ }$element"
    fi
  done