diff --git a/install-plugins.sh b/install-plugins.sh
index d6ac4cc..1bce1bf 100755
--- a/install-plugins.sh
+++ b/install-plugins.sh
@@ -5,9 +5,8 @@
 # FROM jenkins
 # RUN install-plugins.sh docker-slaves github-branch-source
 
-set -e
 
-REF=/usr/share/jenkins/ref/plugins
+REF=${REF:-/usr/share/jenkins/ref/plugins}
 mkdir -p "$REF"
 
 function download() {
@@ -15,7 +14,7 @@
 
 	if [[ ! -f "${plugin}.hpi" ]]; then
 
-		url="${JENKINS_UC}/latest/${plugin}.hpi"
+		local url="${JENKINS_UC}/latest/${plugin}.hpi"
 		echo "download plugin : $plugin from $url"
 
 		curl -s -f -L "$url" -o "${plugin}.hpi"
@@ -23,7 +22,9 @@
 		then
 			# some plugin don't follow the rules about artifact ID
 			# typically: docker-plugin
-			curl -s -f -L "$url" -o "${plugin}-plugin.hpi"
+			local url="${JENKINS_UC}/latest/${plugin}-plugin.hpi"
+			echo "download plugin : $plugin from $url"
+			curl -s -f -L "${url}" -o "${plugin}.hpi"
 			if [[ $? -ne 0 ]]
 			then
 				>&2 echo "failed to download plugin ${plugin}"
@@ -42,7 +43,7 @@
 function resolveDependencies() {	
 	local plugin="$1"; shift
 
-	dependencies=`jrunscript -e '\
+	local dependencies=`jrunscript -e '\
 	java.lang.System.out.println(\
 		new java.util.jar.JarFile("'${plugin}.hpi'")\
 			.getManifest()\
@@ -58,15 +59,14 @@
 	echo " > depends on  ${dependencies}"
 
 	IFS=',' read -a array <<< "${dependencies}"
-
     for d in "${array[@]}"
 	do
-		plugin=$(echo $d | cut -d':' -f1 -)
+		local p=$(echo $d | cut -d':' -f1 -)
 		if [[ $d == *"resolution:=optional"* ]] 
 		then	
-			echo "skipping optional dependency $plugin"
+			echo "skipping optional dependency $p"
 		else
-			download "$plugin"
+			download "$p"
 		fi
 	done
 	touch "${plugin}.resolved"