diff --git a/src/configure.sh b/src/configure.sh
old mode 100644
new mode 100755
index eb7416805aa..03678e013a9
--- a/src/configure.sh
+++ b/src/configure.sh
@@ -3,37 +3,59 @@
 CFG_SRC_DIR=${0%${0##*/}}
 CFG_BUILD_DIR=$PWD
 
-CFG_OSTYPE=$(uname -s)
-CFG_CPUTYPE=$(uname -m)
+echo "configure: recreating config.mk"
+echo '' >config.mk
 
-echo "configuring on $CFG_CPUTYPE $CFG_OSTYPE"
-
-echo "setting up build directories"
-for i in boot/{fe,me,be,driver,util} \
-         rt/{isaac,bigint,sync,test} \
-         stage{0,1,2}                \
-         test/{run-pass,compile-{pass,fail}}
+echo "configure: making directories"
+for i in \
+    boot/fe boot/me boot/be boot/driver boot/util \
+    rt/isaac rt/bigint rt/sync rt/test \
+    stage0 stage1 stage2 \
+    test/run-pass test/compile-pass test/compile-fail
 do
     mkdir -p -v $i
 done
 
-CFG_VALGRIND=$(sh which valgrind)
-CFG_OCAMLC_OPT=$(sh which ocamlc.opt)
-
-echo "copying Makefile"
+echo "configure: copying Makefile"
 cp -v ${CFG_SRC_DIR}Makefile.in ./Makefile
 
-echo "writing config.mk"
-cat >config.mk <<EOF
+putvar() {
+    local T
+    eval T=\$$1
+    printf "%-20s := %s\n" $1 $T
+    printf "%-20s := %s\n" $1 $T >>config.mk
+}
 
-CFG_OSTYPE        := $CFG_OSTYPE
-CFG_CPUTYPE       := $CFG_CPUTYPE
-CFG_SRC_DIR       := $CFG_SRC_DIR
-CFG_BUILD_DIR     := $CFG_BUILD_DIR
+probe() {
+    local V=$1
+    local P=$2
+    local T
+    T=$(which $P 2>&1)
+    if [ $? -ne 0 ]
+    then
+        T=""
+    fi
+    eval $V=\$T
+    putvar $V
+}
 
-CFG_VALGRIND      := $CFG_VALGRIND
-CFG_OCAMLC_OPT    := $CFG_OCAMLC_OPT
+echo "configure: inspecting environment"
 
-EOF
+CFG_OSTYPE=$(uname -s)
+CFG_CPUTYPE=$(uname -m)
 
-echo "configured ok"
+putvar CFG_SRC_DIR
+putvar CFG_BUILD_DIR
+putvar CFG_OSTYPE
+putvar CFG_CPUTYPE
+
+echo "configure: looking for programs"
+probe CFG_VALGRIND         valgrind
+probe CFG_OCAMLC           ocamlc
+probe CFG_OCAMLC_OPT       ocamlc.opt
+probe CFG_OCAMLOPT         ocamlopt
+probe CFG_OCAMLOPT_OPT     ocamlopt.opt
+probe CFG_FLEXLINK         flexlink
+probe CFG_LLVM_CONFIG      llvm-config
+
+echo "configure: complete"