--- /dev/null
+diff --git a/Makefile b/Makefile
+index b2d1a32..3c3639f 100644
+--- a/Makefile
++++ b/Makefile
+@@ -3,22 +3,22 @@ VERSION = 0.4.11
+ SHELL = /bin/sh
+ top_srcdir = .
+ srcdir = .
+-prefix = /usr
+-exec_prefix = ${prefix}
+-
+-bindir = ${exec_prefix}/bin
+-sbindir = ${exec_prefix}/sbin
+-libexecdir = ${exec_prefix}/libexec
+-datadir = ${prefix}/share
+-sysconfdir = ${prefix}/etc
+-sharedstatedir = ${prefix}/com
+-localstatedir = ${prefix}/var
+-libdir = ${exec_prefix}/lib
+-infodir = ${prefix}/info
++prefix ?= /usr
++exec_prefix ?= ${prefix}
++
++bindir ?= ${exec_prefix}/bin
++sbindir ?= ${exec_prefix}/sbin
++libexecdir ?= ${exec_prefix}/libexec
++datadir ?= ${prefix}/share
++sysconfdir ?= ${prefix}/etc
++sharedstatedir ?= ${prefix}/com
++localstatedir ?= ${prefix}/var
++libdir ?= ${exec_prefix}/lib
++infodir ?= ${prefix}/info
+ docdir =
+-includedir = ${prefix}/include
++includedir ?= ${prefix}/include
+ oldincludedir = /usr/include
+-mandir = ${prefix}/share/man
++mandir ?= ${prefix}/share/man
+
+ pkgdatadir = $(datadir)/$(PACKAGE)
+ pkglibdir = $(libdir)/$(PACKAGE)
+diff --git a/bin/Makefile b/bin/Makefile
+index 52c1f50..abef96a 100644
+--- a/bin/Makefile
++++ b/bin/Makefile
+@@ -1,22 +1,22 @@
+ SHELL = /bin/sh
+ top_srcdir = ..
+ srcdir = ../bin
+-prefix = /usr
+-exec_prefix = ${prefix}
+-
+-bindir = ${exec_prefix}/bin
+-sbindir = ${exec_prefix}/sbin
+-libexecdir = ${exec_prefix}/libexec
+-datadir = ${prefix}/share
+-sysconfdir = ${prefix}/etc
+-sharedstatedir = ${prefix}/com
+-localstatedir = ${prefix}/var
+-libdir = ${exec_prefix}/lib
+-infodir = ${prefix}/info
++prefix ?= /usr
++exec_prefix ?= ${prefix}
++
++bindir ?= ${exec_prefix}/bin
++sbindir ?= ${exec_prefix}/sbin
++libexecdir ?= ${exec_prefix}/libexec
++datadir ?= ${prefix}/share
++sysconfdir ?= ${prefix}/etc
++sharedstatedir ?= ${prefix}/com
++localstatedir ?= ${prefix}/var
++libdir ?= ${exec_prefix}/lib
++infodir ?= ${prefix}/info
+ docdir =
+-includedir = ${prefix}/include
++includedir ?= ${prefix}/include
+ oldincludedir = /usr/include
+-mandir = ${prefix}/man
++mandir ?= ${prefix}/man
+
+ pkgdatadir = $(datadir)/$(PACKAGE)
+ pkglibdir = $(libdir)/$(PACKAGE)
+diff --git a/docs/Makefile b/docs/Makefile
+index 0a41179..e128c85 100644
+--- a/docs/Makefile
++++ b/docs/Makefile
+@@ -1,22 +1,22 @@
+ SHELL = /bin/sh
+ top_srcdir = ..
+ srcdir = ../docs
+-prefix = /usr
+-exec_prefix = ${prefix}
+-
+-bindir = ${exec_prefix}/bin
+-sbindir = ${exec_prefix}/sbin
+-libexecdir = ${exec_prefix}/libexec
+-datadir = ${prefix}/share
+-sysconfdir = ${prefix}/etc
+-sharedstatedir = ${prefix}/com
+-localstatedir = ${prefix}/var
+-libdir = ${exec_prefix}/lib
+-infodir = ${prefix}/info
++prefix ?= /usr
++exec_prefix ?= ${prefix}
++
++bindir ?= ${exec_prefix}/bin
++sbindir ?= ${exec_prefix}/sbin
++libexecdir ?= ${exec_prefix}/libexec
++datadir ?= ${prefix}/share
++sysconfdir ?= ${prefix}/etc
++sharedstatedir ?= ${prefix}/com
++localstatedir ?= ${prefix}/var
++libdir ?= ${exec_prefix}/lib
++infodir ?= ${prefix}/info
+ docdir =
+-includedir = ${prefix}/include
++includedir ?= ${prefix}/include
+ oldincludedir = /usr/include
+-mandir = ${datadir}/man
++mandir ?= ${datadir}/man
+
+ pkgdatadir = $(datadir)/$(PACKAGE)
+ pkglibdir = $(libdir)/$(PACKAGE)