-prefix = /usr/local
-exec_prefix = $(prefix)
-bindir = $(DESTDIR)$(exec_prefix)/bin
-libdir = $(DESTDIR)$(exec_prefix)/lib
-datadir = $(DESTDIR)$(prefix)/share
-mandir = $(DESTDIR)$(datadir)/man
-docdir = $(DESTDIR)$(datadir)/doc
+PREFIX = /usr/local
+bindir = $(DESTDIR)$(PREFIX)/bin
+libdir = $(DESTDIR)$(PREFIX)/lib
+datadir = $(DESTDIR)$(PREFIX)/share
+mandir = $(datadir)/man
+docdir = $(datadir)/doc