diff --git a/bin/miaou-bash b/bin/miaou-bash
index 4baa463..8833d30 100755
--- a/bin/miaou-bash
+++ b/bin/miaou-bash
@@ -19,11 +19,12 @@ function on_return {
   fi
 }
 
-# overridden function which permits backtracing of original `return` statement
+# overridden function which permits backtracing of original `exit` statement
 function exit {
   code=${1:-0}
   # >&2 echo "${BASH_SOURCE[2]}: line ${BASH_LINENO[0]}: exit $@"
   >&2 echo "${BASH_SOURCE[2]}:${BASH_LINENO[0]} exit $code"
+  debug "overridden exit $code"
   builtin exit "$code"
 }
 
@@ -34,15 +35,20 @@ function on_exit {
   stack_functions=("${FUNCNAME[@]}")
   stack_sources=("${BASH_SOURCE[@]}")
 
+  # >/dev/tty echo "stack_functionsA ${#stack_functions[@]} ${stack_functions[@]}"
+
   unset 'stack_lines[-1]'
   unset 'stack_lines[-1]'
   unset 'stack_functions[0]'
   unset 'stack_functions[-1]'
-  stack_functions[-1]='<main>'
+
+  # >/dev/tty echo "stack_functionsB ${#stack_functions[@]} ${stack_functions[@]}"
+  [[ "${#stack_functions[@]}" -gt 0 ]] && stack_functions[-1]='<main>'
+
   unset 'stack_sources[0]'
   unset 'stack_sources[-1]'
 
-  if [[ "${stack_functions[1]}" == exit && "${stack_sources[1]}" == "${BASH_SOURCE[0]}" ]]; then
+  if [[ "${#stack_functions[@]}" -gt 1 && "${stack_functions[1]}" == exit && "${stack_sources[1]}" == "${BASH_SOURCE[0]}" ]]; then
     # the exit case scenario
     unset 'stack_functions[1]'
     unset 'stack_sources[1]'
@@ -57,6 +63,8 @@ function on_exit {
   failure_payload=''
 
   if [[ $code -gt 0 ]]; then
+
+    [[ -p /dev/stdout ]] && debug "kill pipe $code !" && >&2 echo "pipe error: original status $code" && kill -SIGPIPE $$
     last_error=$(tail -n1 "$MIAOU_BASH_ERROR")
     last_source=${stack_sources[0]}
     last_source=${last_source//./"\."} # replace '.' with '\.'
@@ -100,10 +108,19 @@ function on_exit {
                 if [[ $code == 1 ]]; then
                   failure_type='SOURCE NOT FOUND'
                   stack_lines[0]=$line
+                  code=128 # change code to 128 to remember this embedded 'source not found' issue!
                 else
                   if [[ $code == 127 ]]; then
                     failure_type='FILE NOT FOUND'
-                    # TODO: print a warning hint in stderr like so: prefer source rather than subshell
+                    regex='\.sh$|\.bash$'
+                    if [[ "$failure_payload" =~ $regex ]]; then
+                      stack_functions[0]="${stack_functions[0]} (hint: prefer source than subshell:1)"
+                      code=129 # change code to 128 to remember this embedded 'source not found' issue!
+                      # >&2 echo "${last_error}"
+                    else
+                      :
+                      # >&2 echo "${last_error}"
+                    fi
                   else
                     failure_type='UNKNOWN NOT FOUND'
                   fi
@@ -118,10 +135,22 @@ function on_exit {
         fi
       fi
     else
-      failure_type='COMMAND'
+      failure_type='UNDEFINED'
       failure_payload="${last_error}"
       regex="^	.*:[0-9]*	.*\$"
-      [[ "$last_error" =~ $regex ]] || failure_traces+=("ERROR $code:") # <undefined>
+      if [[ "$last_error" =~ $regex ]]; then
+        if [[ "${code}" == 128 ]]; then
+          failure_type='SUBSHELL SOURCE NOT FOUND'
+          stack_functions[0]="${stack_functions[0]} (hint: prefer source than subshell:2)"
+        fi
+      else
+        regex='^pipe error:'
+        if [[ "$last_error" =~ $regex ]]; then
+          code=141
+          failure_type='PIPE ERROR'
+        fi
+        failure_traces+=("ERROR $code:") # <undefined>
+      fi
     fi
 
     for i in "${!stack_functions[@]}"; do
@@ -129,22 +158,32 @@ function on_exit {
       failure_traces+=("$stack_detail")
     done
     dump_failure
+    # builtin exit "$code"
   else
     dump_success
   fi
-
   builtin exit "$code"
 }
 
+function debug {
+  $MIAOU_BASH_DEBUG && >/dev/tty echo "*********** DEBUG: $@"
+  true
+}
+
 function dump_failure {
   dump_stderr true
-  $MIAOU_BASH_DEBUG && >/dev/tty echo '---stacktrace---'
-  >&4 echo "CODE: ${code}"
-  >&4 echo "TYPE: ${failure_type}"
-  >&4 echo "PAYLOAD: ${failure_payload}"
+  debug '---stacktrace---'
+  if [[ ${failure_type} == 'SUBSHELL SOURCE NOT FOUND' ]]; then
+    :
+  else
+    >&4 echo "CODE: ${code}"
+    >&4 echo "TYPE: ${failure_type}"
+    >&4 echo "PAYLOAD: ${failure_payload}"
+  fi
   for i in "${failure_traces[@]}"; do
     >&4 echo -e "$i"
   done
+  debug '---end of stacktrace---'
   cleanup
 }
 
@@ -166,7 +205,7 @@ function dump_success {
 }
 
 function cleanup {
-  trap - ERR TERM INT EXIT
+  trap - ERR TERM EXIT DEBUG
   exec 3>&- 4>&-
   rm "$MIAOU_BASH_ERROR"
 }