prefix default value

lib/functions.sh

@@ -4,7 +4,7 @@ function idem_apt_install() {
     if ! (/usr/bin/dpkg-query --status "$i" >/dev/null 2>&1); then
       sudo apt install -y "$i"
     else
-      $VERBOSE && echo "$PREFIX apt package <$i> already installed!"
+      $VERBOSE && echo "${PREFIX:=}apt package <$i> already installed!"
     fi
   done
 }