diff --git a/poc b/poc
index fa26b9c..94a2c4d 100755
--- a/poc
+++ b/poc
@@ -44,11 +44,10 @@ function is_true {
   [[ "${1:-}" == 'true' ]]
 }
 
-# FIXME: define an alias to bypass ARG evaluation when unnecessary!
-# example:
-#   alias toto="bash -c \"[[ \\\$MIAOU_DEBUG == 'true' ]] && echo yes \\\$* || echo nope\""
+# HINT: define an alias to bypass ARG evaluation when unnecessary!
+# example: alias toto="bash -c \"[[ \\\$MIAOU_DEBUG == 'true' ]] && echo yes \\\$* || echo nope\""
 function miaou_debug {
-  is_true "${MIAOU_DEBUG}" && >/dev/tty builtin echo -e "\e[90mDEBUG <==> \e[33m$*\e[0m" || true
+  is_true "${MIAOU_DEBUG}" && >/dev/tty builtin echo -e "\e[90m <== DEBUG ==> \e[33m$*\e[0m" || true
 }
 
 function tty_ansi {
@@ -73,9 +72,8 @@ function on_error {
   failure_code="${1:-200}"
   >/dev/tty printf '\r' # force carriage return explicitly
 
-  miaou_debug "on_error: $failure_code ($$ -- $BASHPID)"
-
   if [[ $$ == "$BASHPID" ]]; then
+    miaou_debug "<on_error exit=$failure_code/>"
     failure_type="COMMAND_ERROR"
     print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" '...'
 
@@ -91,6 +89,7 @@ function on_error {
 
     exit "$failure_code"
   else
+    miaou_debug "<on_error pipe=$failure_code sub_pid=$BASHPID pid=$$/>"
     print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" 'SUBSHELL_ERROR'
     kill -PIPE $$
   fi
@@ -122,22 +121,22 @@ function on_pipe {
     failure_code=141
     failure_type="PIPE_ERROR"
   fi
-  # miaou_debug on_pipe: "${failure_code}"
+  miaou_debug "<on_pipe exit=$failure_code sub_pid=$BASHPID pid=$$/>"
   exit "$failure_code"
 }
 
 function dump_stderr {
-  miaou_debug --stderr--
+  miaou_debug '<stderr>'
   mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
   tty_ansi FG_LIGHTBLUE
   for i in "${tmp_error[@]}"; do echo "$i"; done
   tty_ansi RESET
-  miaou_debug --end of stderr--
+  miaou_debug '</stderr>'
 }
 
 function dump_failure {
   local i
-  miaou_debug --tty error box--
+  miaou_debug '<error_box>'
   tty_ansi FG_MAGENTA
   length_box=$((${#failure_type} + ${#failure_code} + (2 * 2) + 2))
   [[ -v failure_payload ]] && length_box=$((length_box + ${#failure_payload} + (2 * 2) + 1))
@@ -157,11 +156,11 @@ function dump_failure {
   echo '╝'
   echo "     ║"
   tty_ansi RESET
-  miaou_debug --end of tty error box--
+  miaou_debug '</error_box>'
 }
 
 function dump_stacktrace {
-  miaou_debug --stacktrace ${#error_source[@]}--
+  miaou_debug "<stacktrace count=${#error_source[@]}>"
   local i source lineno funcname
   for i in "${!error_source[@]}"; do
     tty_ansi FG_MAGENTA
@@ -176,7 +175,7 @@ function dump_stacktrace {
     printf " \t%s" "$funcname"
     echo
   done
-  miaou_debug --end of stacktrace--
+  miaou_debug '</stacktrace>'
 }
 
 function on_exit {
@@ -188,7 +187,7 @@ function on_exit {
     2>&3 >/dev/tty dump_stacktrace
   fi
 
-  miaou_debug "on_exit $code"
+  miaou_debug "</source type=failure exit=$code pid=${BASHPID}>"
 }
 
 ## main
@@ -204,8 +203,8 @@ trap 'on_error $?' ERR
 trap 'on_exit $?' EXIT
 trap 'on_pipe' PIPE
 
-miaou_debug "--source from ${BASHPID}"
+miaou_debug "<source from=$BASH_ARGV0 pid=${BASHPID}>"
 exec 3>/dev/stderr
 # shellcheck source=/dev/null
 2>"$MIAOU_BASH_ERROR" source "$BASH_ARGV0"
-miaou_debug '--source success'
+miaou_debug "</source type=success pid=${BASHPID}>"