diff --git a/poc b/poc
index 1e3fc4e..3cbb239 100755
--- a/poc
+++ b/poc
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+#!/usr/bin/env -S -- bash
+#!/usr/bin/env -S -- bash -x
 
 # constants
 
@@ -47,7 +48,16 @@ function is_true {
 # 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 "${MIAOU_DEBUG}" && >&4 builtin echo -e "\e[90m <== DEBUG ==> \e[33m$*\e[0m" || true
+  if is_true "${MIAOU_DEBUG}"; then
+    [[ ! -v miaou_debug_hierarchy ]] && miaou_debug_hierarchy=0
+    local i message="$*" padding=''
+    regex='^</' # starts with </
+    [[ $miaou_debug_hierarchy -gt 0 ]] && [[ "${message}" =~ $regex ]] && ((--miaou_debug_hierarchy))
+    for i in $(seq 1 "$miaou_debug_hierarchy"); do padding+='  '; done
+    >&4 builtin echo -e "\e[90m <== DEBUG ==> ${padding}\e[33m${message}\e[0m"
+    regex='^<[^/].*[^/]>$' # markup starting
+    [[ "${message}" =~ $regex ]] && ((++miaou_debug_hierarchy)) || true
+  fi
 }
 
 function on_return {
@@ -59,6 +69,7 @@ function on_return {
     print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
     miaou_debug "<on_return code=$failure_code payload=$failure_payload />"
   fi
+  true
 }
 
 # overridden function which permits backtracing of the original `exit` statement
@@ -77,7 +88,7 @@ function exit {
   failure_type="EXIT"
   failure_payload="${error_funcname[0]}"
 
-  miaou_debug "<exit code=$failure_code overridden/>"
+  miaou_debug "<exit code=$failure_code overridden />"
   print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
   builtin exit "$failure_code"
 }
@@ -105,7 +116,7 @@ function on_error {
   failure_code="${1:-200}"
   >&4 printf '\r' # TODO: force carriage return explicitly, is it really useful?
 
-  miaou_debug "<on_error code=${failure_code} command=[${BASH_COMMAND}]>"
+  miaou_debug "<on_error code=${failure_code} command={${BASH_COMMAND}}>"
 
   if [[ $$ == "$BASHPID" ]]; then
     if [[ ! -v failure_type ]]; then
@@ -129,14 +140,14 @@ function on_error {
     error_funcname=("${error_funcname[@]}")
 
     if [[ -v failure_payload ]]; then
-      miaou_debug "</on_error exit=$failure_code type=${failure_type} payload=${failure_payload}>"
+      miaou_debug "</on_error exit=$failure_code type=${failure_type} payload={${failure_payload}} >"
     else
-      miaou_debug "</on_error exit=$failure_code type=${failure_type}>"
+      miaou_debug "</on_error exit=$failure_code type=${failure_type} >"
     fi
 
     builtin exit "$failure_code"
   else
-    miaou_debug "</on_error pipe=$failure_code sub_pid=$BASHPID pid=$$ command='${BASH_COMMAND}'>"
+    miaou_debug "</on_error pipe=$failure_code sub_pid=$BASHPID pid=$$ command={${BASH_COMMAND}}>"
     print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" 'SUBSHELL_ERROR' "${BASH_COMMAND}"
     kill -PIPE $$
   fi
@@ -169,7 +180,7 @@ function on_pipe {
     failure_code=141
     failure_type="PIPE_ERROR"
   fi
-  miaou_debug "<on_pipe exit=$failure_code sub_pid=$BASHPID pid=$$/>"
+  miaou_debug "<on_pipe code=$failure_code sub_pid=$BASHPID pid=$$ />"
   builtin exit "$failure_code"
 }
 
@@ -207,7 +218,7 @@ function dump_failure {
 }
 
 function dump_stacktrace {
-  miaou_debug "<stacktrace count=${#error_source[@]}>"
+  miaou_debug "<stacktrace count=${#error_source[@]} >"
   local i source lineno funcname
   for i in "${!error_source[@]}"; do
     tty_ansi FG_MAGENTA
@@ -229,7 +240,7 @@ function on_exit {
   trap - RETURN
   local code="${1:-0}" last_error regex
 
-  miaou_debug "<on_exit code=$code>"
+  miaou_debug "<on_exit code=$code >"
 
   [[ ! -v tmp_error ]] && mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
 
@@ -237,7 +248,7 @@ function on_exit {
     last_error="${tmp_error[-1]}"
     regex='^(.*): line ([0-9]+): miaou_error: RETURN [0-9]+'
     if [[ "$last_error" =~ $regex ]]; then
-      miaou_debug "<return exit=$code />"
+      miaou_debug "<return code=$code />"
       local source line
       source="${BASH_REMATCH[1]}"
       line="${BASH_REMATCH[2]}"
@@ -251,7 +262,7 @@ function on_exit {
   else
     if [[ $code -gt 0 && ${#tmp_error[@]} -gt 0 ]]; then
       last_error="${tmp_error[-1]}"
-      miaou_debug "<on_exit_tmp_error last='$last_error'>"
+      miaou_debug "<on_exit_tmp_error last={$last_error} >"
       if [[ $code -eq 1 ]]; then
         regex='^(.*): line ([0-9]+): (.*): unbound variable$'
         if [[ "$last_error" =~ $regex ]]; then
@@ -259,7 +270,7 @@ function on_exit {
           source="${BASH_REMATCH[1]}"
           line="${BASH_REMATCH[2]}"
           payload="${BASH_REMATCH[3]}"
-          miaou_debug "<unbound_variable source=${source} line=${line} payload=${payload}>"
+          miaou_debug "<unbound_variable source=${source} line=${line} payload={${payload}} >"
           failure_code=$code
           failure_type='UNBOUND_VARIABLE'
           failure_payload="${BASH_REMATCH[3]}"
@@ -284,9 +295,9 @@ function on_exit {
     2>&3 >&4 dump_stacktrace
   fi
   if [[ $code -gt 0 ]]; then
-    miaou_debug "</on_exit exit=$code>"
+    miaou_debug "</on_exit exit=$code >"
   else
-    miaou_debug "</on_exit success>"
+    miaou_debug "</on_exit success >"
   fi
 }