diff -rU4 disper-orig/Makefile disper/Makefile

--- disper-orig/Makefile	2011-09-09 16:27:16.000000000 +0200

+++ disper/Makefile	2014-09-17 20:54:48.310555843 +0200

@@ -1,9 +1,17 @@

 # simple Makefile for disper

-PREFIX = /usr/local

-BINDIR = $(PREFIX)/bin

-DATADIR = $(PREFIX)/share/disper

+$(if $(strip $(PREFIX)),,$(PREFIX=/usr/local))

+$(if $(strip $(BINDIR)),,$(BINDIR=$(PREFIX)/bin))

+$(if $(strip $(DATADIR)),,$(DATADIR=$(PREFIX)/share))

+

+$(warning $(value $PREFIX))

+$(warning $(value BINDIR))

+$(warning $(value DATADIR))

+

+DATADIR := $(join $(DATADIR), /disper)

+

+$(warning $(value DATADIR))

 INSTALL = install

 all: disper disper.1