diff --git a/tools/miaou-exec b/tools/miaou-exec
index e491342..1e9b320 100755
--- a/tools/miaou-exec
+++ b/tools/miaou-exec
@@ -41,15 +41,20 @@ function parse_options {
   done
   [[ ! -v CONTAINER ]] && usage && exit 1
   if [[ -t 0 ]]; then
-    ((${#COMMAND_LINE[@]} == 0)) && usage && exit 2
+    echo "${COMMAND_LINE[@]}"
+    echo "${#COMMAND_LINE[@]}"
+    if [[ "${#COMMAND_LINE[@]}" == 0 ]]; then
+      usage
+      builtin exit 2
+    fi
   else
-    HEREDOC=true
+    HEREDOC_OR_PIPE=true
   fi
 
 }
 
 function exec {
-  if [[ -v HEREDOC ]]; then
+  if [[ -v HEREDOC_OR_PIPE ]]; then
     # TODO: test whether miaou-bash mounted within container
     script="miaou-bash <<EOF
     $(cat)