--- a/configure
+++ b/configure
@@ -15,20 +15,19 @@
 LC_ALL=C
 export LC_ALL
 srcdir=
-prefix=/usr/local
+prefix?=/usr/local
 exec_prefix='$(prefix)'
 bindir='$(exec_prefix)/bin'
 datarootdir='$(prefix)/share'
 infodir='$(datarootdir)/info'
 mandir='$(datarootdir)/man'
-CXX=g++
+CXX?=g++
 CPPFLAGS=
-CXXFLAGS='-Wall -W -O2'
-LDFLAGS=
+CXXFLAGS?='-Wall -W -O2'
+LDFLAGS?=
 MAKEINFO=makeinfo
 
 # checking whether we are using GNU C++.
-/bin/sh -c "${CXX} --version" > /dev/null 2>&1 || { CXX=c++ ; CXXFLAGS=-O2 ; }
 
 # Loop over all args
 args=