diff --git a/bin/miaou-bash b/bin/miaou-bash
index e00ceaa..677a1c4 100755
--- a/bin/miaou-bash
+++ b/bin/miaou-bash
@@ -1,302 +1,428 @@
-#!/usr/bin/env bash
+#!/usr/bin/env -S -- bash
+#!/usr/bin/env -S -- bash -x
 
-# CONSTANTS
+# constants
 
-MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$(id -u)")
+MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$UID")
 MIAOU_DEBUG=${MIAOU_DEBUG:-false}
-readonly MIAOU_BASH_ERROR MIAOU_DEBUG
 
-# FUNCTIONS
+declare -A ANSI
+ANSI[RESET]=0
+
+ANSI[STYLE_ITALIC]=3
+ANSI[STYLE_BOLD]=1
+ANSI[STYLE_UNDERLINE]=4
+ANSI[STYLE_STRIKETHROUGH]=9
+
+ANSI[FG_BLACK]=30
+ANSI[FG_RED]=31
+ANSI[FG_GREEN]=32
+ANSI[FG_YELLOW]=33
+ANSI[FG_BLUE]=34
+ANSI[FG_PURPLE]=35
+ANSI[FG_CYAN]=36
+ANSI[FG_WHITE]=37
+ANSI[FG_GRAY]=90
+ANSI[FG_LIGHTBLUE]=94
+ANSI[FG_MAGENTA]=95
+
+ANSI[BG_BLACK]=40
+ANSI[BG_RED]=41
+ANSI[BG_GREEN]=42
+ANSI[BG_YELLOW]=43
+ANSI[BG_BLUE]=44
+ANSI[BG_PURPLE]=45
+ANSI[BG_CYAN]=46
+ANSI[BG_WHITE]=47
+ANSI[BG_GRAY]=90
+ANSI[BG_MAGENTA]=95
+
+readonly MIAOU_BASH_ERROR MIAOU_DEBUG ANSI
+
+## functions
 
 function is_true {
-  [[ "${1,,}" =~ ^true$ ]] #${1,,} => Lowercase all chars
+  [[ "${1:-}" == 'true' ]]
 }
 
-# overridden function which permits backtracing of original `return` statement
-function false {
-  >&2 echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]} false"
-  miaou_debug "overridden false"
-  builtin false
-}
-
-# 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[1]}:${BASH_LINENO[0]} exit $code"
-  miaou_debug "overridden exit $code"
-  builtin exit "$code"
-}
-
-function on_usr1 {
-  cleanup
-  # FIXME: get exit code from MIAOU_BASH_SUBERROR
-  builtin exit 1
+# 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 {
+  if is_true "${MIAOU_DEBUG}"; then
+    local i message="$*" padding=''
+    local compute_hierarchy=true
+    [[ ! -v miaou_debug_hierarchy ]] && miaou_debug_hierarchy=0
+
+    regex='^</' # starts with </
+    [[ $miaou_debug_hierarchy -gt 0 ]] &&
+      [[ "${message}" =~ $regex ]] &&
+      miaou_debug_hierarchy=$((miaou_debug_hierarchy - 1)) &&
+      compute_hierarchy=false
+
+    for ((i = 0; i < miaou_debug_hierarchy; i++)); do padding+='  '; done
+    >&4 builtin echo -e "\e[90m <== DEBUG ==> ${padding}\e[33m${message}\e[0m"
+
+    regex='[^/]>$' # does NOT end with />
+    is_true $compute_hierarchy &&
+      [[ "${message}" =~ $regex ]] &&
+      miaou_debug_hierarchy=$((miaou_debug_hierarchy + 1)) ||
+      true
+  fi
 }
 
 function on_return {
-  # regex does not work here unfortunately!
-  if [[ "${BASH_COMMAND}" == 'return '* ]]; then
-    code=$(echo "${BASH_COMMAND}" | cut -d' ' -f2)
-    if [[ -n "$code" ]] && [[ "$code" -ne 0 ]]; then
-      trap - DEBUG
-      >&2 echo "${BASH_SOURCE[2]}: line ${BASH_LINENO[0]}: return $code from ${FUNCNAME[1]}"
-    fi
+  local regex='return ([0-9]+)'
+  if [[ "$BASH_COMMAND" =~ $regex ]] && [[ "${BASH_REMATCH[1]}" -gt 0 ]]; then
+    failure_code="${BASH_REMATCH[1]}"
+    failure_type="RETURN"
+    failure_payload="${FUNCNAME[0]}"
+    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
 }
 
-function on_exit {
-  code=${1:-0}
-
-  if [[ $code -gt 0 ]]; then
-
-    stack_lines=("${BASH_LINENO[@]}")
-    stack_functions=("${FUNCNAME[@]}")
-    stack_sources=("${BASH_SOURCE[@]}")
-
-    unset 'stack_lines[-1]'
-    unset 'stack_lines[-1]'
-    unset 'stack_functions[0]'
-    unset 'stack_functions[-1]'
-
-    [[ "${#stack_functions[@]}" -gt 0 ]] && stack_functions[-1]='<main>'
-
-    unset 'stack_sources[0]'
-    unset 'stack_sources[-1]'
+# overridden function which permits backtracing of the original `exit` statement
+function exit {
+  error_source=("${BASH_SOURCE[@]}")
+  error_lineno=("${BASH_LINENO[@]}")
+  error_funcname=("${FUNCNAME[@]}")
+  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+  unset 'error_source[0]' 'error_lineno[-1]' 'error_funcname[0]'
+  error_funcname[-1]='<main>'
+  error_source=("${error_source[@]}")
+  error_lineno=("${error_lineno[@]}")
+  error_funcname=("${error_funcname[@]}")
+
+  failure_code=${1:-0}
+  failure_type="EXIT"
+  failure_payload="${error_funcname[0]}"
+
+  miaou_debug "<exit code=$failure_code overridden/>"
+  print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
+  builtin exit "$failure_code"
+}
 
-    if [[ "${#stack_functions[@]}" -gt 1 && "${stack_functions[1]}" =~ exit|false && "${stack_sources[1]}" == "${BASH_SOURCE[0]}" ]]; then
-      # the exit or false case scenario
-      unset 'stack_functions[1]'
-      unset 'stack_sources[1]'
-      unset 'stack_lines[0]'
+function tty_ansi {
+  local code
+  for code in "$@"; do
+    if [[ -v ANSI[$code] ]]; then
+      >&4 echo -ne "\e[${ANSI[$code]}m"
+    else
+      >&2 echo "unknown ansi key: <$code>"
+      break
     fi
+  done
+}
 
-    stack_lines=("${stack_lines[@]}")
-    stack_functions=("${stack_functions[@]}")
-    stack_sources=("${stack_sources[@]}")
-
-    failure_payload=''
+function print_miaou_error {
+  local source="$1" line="$2" code="$3" type="$4" payload="${5:-}"
+  local message
+  message="${source}: line ${line}: miaou_error: ${type} ${code}"
+  [[ -n "$payload" ]] && message+=" payload: ${payload}"
+  >&2 echo "$message"
+}
 
-    last_error=$(tail -n1 "$MIAOU_BASH_ERROR")
-    last_source=${stack_sources[0]}
-    last_source=${last_source//./"\."} # replace '.' with '\.'
-    regex1="^$last_source: line ([0-9]+): (.*)\$"
-    regex2="^$last_source:([0-9]+) (.*)\$"
+function add_miaou_error {
+  local source="$1" line="$2" code="$3" type="$4" payload="${5:-}"
+  local message
+  message="${source}: line ${line}: miaou_error: ${type} ${code}"
+  [[ -n "$payload" ]] && message+=" payload: ${payload}"
+  tmp_error+=("$message")
+}
 
-    # FIXME: too much tricky! (delayed stderr)
-    if [[ -p /dev/stdout ]]; then
-      failure_type='SUBSHELL_TERM'
-      failure_payload="$last_error"
+function on_error {
+  trap - RETURN
+  failure_code="${1:-200}"
+  >&4 printf '\r' # TODO: force carriage return explicitly, is it really useful?
 
-      if [[ "$last_error" =~ $regex1 || "$last_error" =~ $regex2 ]]; then
-        failure_payload="${BASH_REMATCH[2]}"
-      fi
-      last_error="${BASH_SOURCE[1]}:${BASH_LINENO[0]} subshell term $code"
-      printf "\r" # useful!
-      kill -USR1 $$
-    else
-      failure_type='UNKNOWN'
-    fi
+  miaou_debug "<on_error code=${failure_code} command={${BASH_COMMAND}}>"
 
-    # debug "last_error=[$last_error] <=> ${last_source}"
-    if [[ "$last_error" =~ $regex1 || "$last_error" =~ $regex2 ]]; then
-      line=${BASH_REMATCH[1]}
-      message=${BASH_REMATCH[2]}
-      regex='^(.*): unbound variable$'
-      if [[ $code == 1 ]] && [[ "$message" =~ $regex ]]; then
-        failure_type='UNBOUND_VARIABLE'
-        failure_payload="${BASH_REMATCH[1]}"
-        stack_lines[0]=$line
+  if [[ $$ == "$BASHPID" ]]; then
+    if [[ ! -v failure_type ]]; then
+      if [[ ${BASH_COMMAND} == 'false' ]]; then
+        failure_type="FALSE"
+        print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}"
       else
-        if [[ "$message" == 'false' ]]; then
-          failure_type='FALSE'
-        else
-          regex="^return ([0-9]*) from (.*)\$"
-          if [[ "$message" =~ $regex ]]; then
-            # return_code="${BASH_REMATCH[1]}"
-            funcname="${BASH_REMATCH[2]}"
-            # >&4 echo "RETURN DETECTED line ${stack_sources[0]} $line $funcname"
-            stack_sources=("${stack_sources[0]}" "${stack_sources[@]}")
-            stack_lines=("$line" "${stack_lines[@]}")
-            stack_functions=("$funcname" "${stack_functions[@]}")
-
-            failure_type='RETURN'
+        failure_type="COMMAND_ERROR"
+        failure_payload="${BASH_COMMAND}"
+        print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
+
+        miaou_debug "<investigate_tmp_error pid=${BASHPID}>"
+        load_tmp_error # cannot print_miaou_error after investigation
+
+        if [[ ${#tmp_error[@]} -gt 1 ]]; then
+          local last_error regex
+          last_error="${tmp_error[-2]}" # the second latest cause previous print_miaou_error above
+
+          regex='^(.*): line ([0-9]+): (.*): command not found$'
+          if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
+            failure_type='COMMAND_NOT_FOUND'
+            failure_payload="${BASH_REMATCH[3]}"
+            miaou_debug "<command_not_found payload=${failure_payload}/>"
           else
-            regex='^(.*): command not found$'
-            if [[ "$message" =~ $regex ]]; then
-              failure_type='COMMAND_NOT_FOUND'
-              failure_payload="${BASH_REMATCH[1]}"
-            else
-              regex='^exit'
-              if [[ "$message" =~ $regex ]]; then
-                failure_type='EXIT'
-              else
-                regex='^(.*): No such file or directory$'
-                if [[ "$message" =~ $regex ]]; then
-                  failure_payload="${BASH_REMATCH[1]}"
-                  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 [[ $code == 127 ]]; then
-                      failure_type='FILE_NOT_FOUND'
-                      regex='\.sh$|\.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
-                  fi
-                fi
-              fi
+            regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
+            if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
+              failure_type='FILE_NOT_FOUND'
+              failure_payload="${BASH_REMATCH[3]}"
+              miaou_debug "<file_not_found payload=${failure_payload}/>"
             fi
           fi
         fi
-      fi
-    else
-      failure_payload="${last_error}"
-      regex="╟─⟶"
-      if [[ "$last_error" =~ $regex ]]; then
-        last_trim=false # keep the last error for next stacktrace
-        error_block=false
-        failure_type='SUBSHELL_ERROR'
-        #
-        # >&4 echo "SUBSHELL_ERROR caught up ${BASH_SOURCE[*]} ${BASH_LINENO[*]}"
-        #
-        stack_functions[0]="${stack_functions[0]} (hint: prefer source than subshell)"
-        [[ "${code}" == 128 ]] && failure_type='SUBSHELL_SOURCE_NOT_FOUND'
-      else
-        failure_type='COMMAND_ERROR'
+        miaou_debug '</investigate_tmp_error>'
       fi
     fi
 
-    dump_failure "${last_trim:-true}" "${error_block:-true}"
+    error_source=("${BASH_SOURCE[@]}")
+    error_lineno=("${BASH_LINENO[@]}")
+    error_funcname=("${FUNCNAME[@]}")
+    unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+    unset 'error_source[0]' 'error_lineno[-1]' 'error_funcname[0]'
+    error_funcname[-1]='<main>'
+    error_source=("${error_source[@]}")
+    error_lineno=("${error_lineno[@]}")
+    error_funcname=("${error_funcname[@]}")
+
+    if [[ -v failure_payload ]]; then
+      miaou_debug "</on_error exit=$failure_code type=${failure_type} payload={${failure_payload}}>"
+    else
+      miaou_debug "</on_error exit=$failure_code type=${failure_type}>"
+    fi
+    builtin exit "$failure_code"
   else
-    dump_success
+    print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" 'SUBSHELL_ERROR' "${BASH_COMMAND}"
+    miaou_debug "</on_error pipe=$failure_code sub_pid=$BASHPID pid=$$ command={${BASH_COMMAND}}>"
+    kill -PIPE $$
   fi
+}
 
-  # FIXME: be aware of errors during the on_exit function because it does not pop up!
-  miaou_debug "--end of on_exit => $code --"
+function populate_error_arrays {
 
-  builtin exit "$code"
+  local source=$1 line=$2 payload=$3
+  unset 'error_source[0]' 'error_lineno[0]' 'error_funcname[0]'
+  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+  error_source=("$source" "${error_source[@]}")
+  error_lineno=("$line" "${error_lineno[@]}")
+  error_funcname=("${error_funcname[@]}" '<main>')
 }
 
-function miaou_debug {
-  is_true "${MIAOU_DEBUG}" && >/dev/tty builtin echo -e "*********** DEBUG: $*" || true
+function on_pipe {
+  trap - RETURN
+  local tmp_error regex source lineno
+  miaou_debug "<on_pipe sub_pid=$BASHPID pid=$$>"
+
+  error_source=("${BASH_SOURCE[@]}")
+  error_lineno=("${BASH_LINENO[@]}")
+  error_funcname=("${FUNCNAME[@]}")
+  unset 'error_source[0]' 'error_lineno[0]' 'error_funcname[0]'
+  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
+
+  load_tmp_error
+  last_error="${tmp_error[-1]}"
+
+  regex='^(.*): line ([0-9]+): miaou_error: SUBSHELL_ERROR ([0-9]+) payload: (.*)$'
+  if [[ $last_error =~ $regex ]]; then
+    source=${BASH_REMATCH[1]}
+    lineno=${BASH_REMATCH[2]}
+    failure_code=${BASH_REMATCH[3]}
+    failure_payload=${BASH_REMATCH[4]}
+    failure_type="SUBSHELL_ERROR"
+    miaou_debug "<subshell_error payload={${failure_payload}}"
+    error_source=("$source" "${error_source[@]}")
+    error_lineno=("$lineno" "${error_lineno[@]}")
+    error_funcname=("${error_funcname[@]}" '<main>')
+  else
+    failure_code=141
+    failure_type="PIPE_ERROR"
+  fi
+  miaou_debug "</on_pipe>"
+  builtin exit "$failure_code"
 }
 
-function ansi_block_continuation {
-  tput sc
-  tput cuu 1
-  BG=RED FG=BLACK style_ansi "\t╦"
-  tput rc
-  FG=RED style_ansi "\t║\n"
+function dump_stderr {
+  miaou_debug "<stderr count=${#tmp_error[@]}>"
+  tty_ansi FG_LIGHTBLUE
+  for i in "${tmp_error[@]}"; do echo "$i"; done
+  tty_ansi RESET
+  miaou_debug '</stderr>'
 }
 
-function ansi_block_error {
-  FG=BLACK
-  BG=RED
-  local content detail exit_code
+function dump_failure {
+  local i
+  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))
+  echo -n '╔'
+  for ((i = 0; i < length_box; i++)); do echo -n '═'; done
+  echo '╗'
+  echo -n "║ $failure_type "
+  [[ -v failure_payload ]] && echo -n ' ' && tty_ansi BG_WHITE FG_BLACK && echo -n "  $failure_payload  " && tty_ansi RESET
+  tty_ansi FG_YELLOW
+  printf "%5s" "  $failure_code  "
+  tty_ansi FG_MAGENTA
+  echo "║"
+
+  if [[ ! -v error_source ]]; then
+    echo -n '╚'
+    for ((i = 0; i < length_box; i++)); do echo -n '═'; done
+    echo '╝'
+    miaou_debug '<continuation disabled/>'
+  else
+    echo -n '╚'
+    for ((i = 0; i < 4; i++)); do echo -n '═'; done
+    echo -n '╦'
+    for ((i = 5; i < length_box; i++)); do echo -n '═'; done
+    echo '╝'
+    echo "     ║"
+    miaou_debug '<continuation enabled/>'
+  fi
+  tty_ansi RESET
+  miaou_debug '</error_box>'
+}
 
-  content=$(style_ansi "$1")
-  content=$(PADDING=2 style_padding "$content")
+function dump_stacktrace {
+  miaou_debug "<stacktrace count=${#error_source[@]}>"
+  local i source lineno funcname
+  for i in "${!error_source[@]}"; do
+    tty_ansi FG_MAGENTA
+    echo -n "     ╟──▷"
+    [[ $i -gt 0 ]] && tty_ansi FG_GRAY
+    tty_ansi STYLE_ITALIC
+    source="${error_source[$i]}"
+    lineno="${error_lineno[$i]}"
+    funcname="${error_funcname[$i]}"
+    printf "%40s:%.4s" "$source" "$lineno"
+    tty_ansi RESET
+    printf " \t%s" "$funcname"
+    echo
+  done
+  miaou_debug '</stacktrace>'
+}
 
-  detail="$2"
-  [[ -n "$detail" ]] && detail=$(BG=BLACK FG=WHITE PADDING=2 style_padding "$2")
+function load_tmp_error {
+  [[ -v tmp_error ]] && return 0
 
-  exit_code=$(FG=CYAN PADDING=2 style_padding "$3")
-  builtin echo -en "\r"
-  BLOCK_CONTINUATION_COL=5 style_block "$content$detail$exit_code"
-  ansi_reset
-  FG=RED style_ansi "     ║" && builtin echo
+  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
+  local count=${#tmp_error[@]}
+  if [[ $count == 0 ]]; then
+    miaou_debug "<tmp_error empty/>"
+  else
+    miaou_debug "<tmp_error count=${count}/>"
+  fi
 }
 
-function ansi_traces {
-  local optional location sources lines functions
-  declare -n sources=$1
-  declare -n lines=$2
-  declare -n functions=$3
-  optional=false
-  for i in "${!sources[@]}"; do
-    FG=RED style_ansi "     ╟─⟶ "
-    location=$(printf "%40s" "${sources[$i]}:${lines[$i]}")
-    is_true "$optional" &&
-      location=$(FG=GRAY STYLE=ITALIC style_ansi "$location") ||
-      location=$(STYLE=ITALIC style_ansi "$location")
-    builtin echo "${location}    ${functions[$i]}"
-    optional=true
-  done
-}
-function dump_failure {
-  declare -F style_ansi >/dev/null || source "$MIAOU_BASH_DIR/lib/ansi.bash"
-  dump_stderr "${1:-true}"
-
-  local error_block="${2:-true}"
-  if is_true $error_block; then
-    miaou_debug "---error box ${failure_type:-} ---"
-    if [[ ${failure_type} == 'SUBSHELL SOURCE NOT FOUND' ]]; then
-      :
+function on_exit {
+  trap - RETURN
+  failure_code="${1:-0}"
+  local last_error regex
+  miaou_debug "<on_exit code=$failure_code>"
+
+  load_tmp_error
+
+  if [[ -v failure_type && "$failure_type" == 'RETURN' ]]; then
+    last_error="${tmp_error[-1]}"
+    regex='^(.*): line ([0-9]+): miaou_error: RETURN [0-9]+'
+    if [[ "$last_error" =~ $regex ]]; then
+      miaou_debug "<return code=$failure_code/>"
+      local source line
+      source="${BASH_REMATCH[1]}"
+      line="${BASH_REMATCH[2]}"
+      error_source=("$source" "${error_source[@]}")
+      error_lineno=("$line" "${error_lineno[@]}")
+      error_funcname=("$failure_payload" "${error_funcname[@]}")
     else
-      >&4 ansi_block_error "$failure_type" "$failure_payload" "$code"
+      miaou_debug "<return type=unexpected/>"
     fi
-    miaou_debug '---end of error box---'
-  fi
 
-  miaou_debug '---stacktrace---'
-  >&4 ansi_traces stack_sources stack_lines stack_functions
-  miaou_debug '---end of stacktrace---'
+  elif [[ -v failure_type && "$failure_type" == 'COMMAND_NOT_FOUND' ]]; then
+    unset 'tmp_error[-1]' 'tmp_error[-1]'
+    add_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
+    miaou_debug '<command_not_found change_stderr />'
 
-  cleanup
-}
+  elif [[ -v failure_type && "$failure_type" == 'FILE_NOT_FOUND' ]]; then
+    unset 'tmp_error[-1]' 'tmp_error[-1]'
+    add_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
+    miaou_debug '<file_not_found change_stderr />'
 
-function dump_stderr {
-  last_trim=${1:-false}
-  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
-  is_true "$last_trim" && unset 'tmp_error[-1]' && tmp_error=("${tmp_error[@]}")
-  if [[ "${#tmp_error[@]}" -gt 0 ]]; then
-    miaou_debug '---stderr---'
-    >&4 printf '\r'
-    for i in "${tmp_error[@]}"; do
-      >&4 echo -e "$i"
-    done
-  else
-    miaou_debug '---no stderr---'
+  elif [[ ! -v failure_type ]]; then
+    if [[ $failure_code -gt 0 && ${#tmp_error[@]} -gt 0 ]]; then
+      last_error="${tmp_error[-1]}"
+      miaou_debug "<investigate_tmp_error last={$last_error}>"
+
+      regex='^(.*): line ([0-9]+): (.*): unbound variable$'
+      if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
+        failure_type='UNBOUND_VARIABLE'
+        failure_payload="${BASH_REMATCH[3]}"
+        failure_code=2
+
+        local source="${BASH_REMATCH[1]}" line="${BASH_REMATCH[2]}"
+        error_source=("${BASH_SOURCE[@]}")
+        error_lineno=("${BASH_LINENO[@]}")
+        error_funcname=("${FUNCNAME[@]}")
+        populate_error_arrays "$source" "$line" "$failure_payload"
+
+        unset 'tmp_error[-1]'
+        add_miaou_error "$source" "$line" "${failure_code}" "${failure_type}" "${failure_payload}"
+        miaou_debug "<unbound_variable source=${source} line=${line} payload=${failure_payload}/>"
+      else
+        regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
+        if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
+          failure_type='SOURCE_NOT_FOUND'
+          failure_payload="${BASH_REMATCH[3]}"
+          failure_code=3
+
+          local source="${BASH_REMATCH[1]}" line="${BASH_REMATCH[2]}"
+          error_source=("${BASH_SOURCE[@]}")
+          error_lineno=("${BASH_LINENO[@]}")
+          error_funcname=("${FUNCNAME[@]}")
+          populate_error_arrays "$source" "$line" "$failure_payload"
+
+          unset 'tmp_error[-1]'
+          add_miaou_error "$source" "$line" "${failure_code}" "${failure_type}" "${failure_payload}"
+          miaou_debug "<source_not_found source=${source} line=${line} payload=${failure_payload}/>"
+        else
+          failure_type='UNKNOWN ERROR'
+          failure_payload="$BASH_COMMAND"
+        fi
+      fi
+      miaou_debug "</investigate_tmp_error>"
+    fi
   fi
-}
 
-function dump_success {
-  dump_stderr
-  cleanup
+  2>&3 >&3 dump_stderr
+  if [[ -v failure_type ]]; then
+    2>&3 >&4 dump_failure
+    if [[ -v error_source ]]; then
+      2>&3 >&4 dump_stacktrace
+    fi
+  fi
+  if [[ $failure_code -gt 0 ]]; then
+    miaou_debug "</on_exit code=$failure_code>"
+  else
+    miaou_debug "</on_exit success>"
+  fi
 }
 
-function cleanup {
-  trap - ERR TERM EXIT DEBUG USR1
-  exec 3>&- 4>&-
-  rm "$MIAOU_BASH_ERROR"
-}
+## main
 
-# MAIN
+set -euo pipefail
+set -E # HALT on subshell error
+set -T # DEBUG RETURN
 
-set -TEue -o pipefail
 [[ $# -lt 1 ]] && >&2 echo 'ERROR: script expected!' && builtin exit 1
-
-# trap 'on_exit $?' ERR TERM INT EXIT
-trap 'on_exit $?' ERR EXIT
-trap 'on_return' DEBUG
-trap 'on_usr1' USR1
 BASH_ARGV0="$1" && shift # to pretend script runs by itself
 
-# magic FD + delayed tee => /dev/fd/3 means delayed stderr, /dev/fd/4 remains original stderr
-exec 3> >(tee "$MIAOU_BASH_ERROR" >/dev/null) 4>/dev/stderr
+trap 'on_error $?' ERR
+trap 'on_exit $?' EXIT
+trap 'on_pipe' PIPE
+trap 'on_return' RETURN
+
+if [[ -e /proc/$$/fd/3 ]]; then exec 4>&3 3>&-; else exec 4>/dev/tty; fi # swap fd 3 4 when fd 3 sent off
+exec 3>/dev/stderr 2>"$MIAOU_BASH_ERROR"
 
-miaou_debug "---stdout--$$ $BASHPID $PPID--"
+miaou_debug "<source file=$BASH_ARGV0 pid=${BASHPID}/>"
 # shellcheck source=/dev/null
-source "$BASH_ARGV0" 2>&3
-dump_success
+source "$BASH_ARGV0"
diff --git a/bin/miaou-bash-old b/bin/miaou-bash-old
new file mode 100755
index 0000000..e00ceaa
--- /dev/null
+++ b/bin/miaou-bash-old
@@ -0,0 +1,302 @@
+#!/usr/bin/env bash
+
+# CONSTANTS
+
+MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$(id -u)")
+MIAOU_DEBUG=${MIAOU_DEBUG:-false}
+readonly MIAOU_BASH_ERROR MIAOU_DEBUG
+
+# FUNCTIONS
+
+function is_true {
+  [[ "${1,,}" =~ ^true$ ]] #${1,,} => Lowercase all chars
+}
+
+# overridden function which permits backtracing of original `return` statement
+function false {
+  >&2 echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]} false"
+  miaou_debug "overridden false"
+  builtin false
+}
+
+# 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[1]}:${BASH_LINENO[0]} exit $code"
+  miaou_debug "overridden exit $code"
+  builtin exit "$code"
+}
+
+function on_usr1 {
+  cleanup
+  # FIXME: get exit code from MIAOU_BASH_SUBERROR
+  builtin exit 1
+}
+
+function on_return {
+  # regex does not work here unfortunately!
+  if [[ "${BASH_COMMAND}" == 'return '* ]]; then
+    code=$(echo "${BASH_COMMAND}" | cut -d' ' -f2)
+    if [[ -n "$code" ]] && [[ "$code" -ne 0 ]]; then
+      trap - DEBUG
+      >&2 echo "${BASH_SOURCE[2]}: line ${BASH_LINENO[0]}: return $code from ${FUNCNAME[1]}"
+    fi
+  fi
+}
+
+function on_exit {
+  code=${1:-0}
+
+  if [[ $code -gt 0 ]]; then
+
+    stack_lines=("${BASH_LINENO[@]}")
+    stack_functions=("${FUNCNAME[@]}")
+    stack_sources=("${BASH_SOURCE[@]}")
+
+    unset 'stack_lines[-1]'
+    unset 'stack_lines[-1]'
+    unset 'stack_functions[0]'
+    unset 'stack_functions[-1]'
+
+    [[ "${#stack_functions[@]}" -gt 0 ]] && stack_functions[-1]='<main>'
+
+    unset 'stack_sources[0]'
+    unset 'stack_sources[-1]'
+
+    if [[ "${#stack_functions[@]}" -gt 1 && "${stack_functions[1]}" =~ exit|false && "${stack_sources[1]}" == "${BASH_SOURCE[0]}" ]]; then
+      # the exit or false case scenario
+      unset 'stack_functions[1]'
+      unset 'stack_sources[1]'
+      unset 'stack_lines[0]'
+    fi
+
+    stack_lines=("${stack_lines[@]}")
+    stack_functions=("${stack_functions[@]}")
+    stack_sources=("${stack_sources[@]}")
+
+    failure_payload=''
+
+    last_error=$(tail -n1 "$MIAOU_BASH_ERROR")
+    last_source=${stack_sources[0]}
+    last_source=${last_source//./"\."} # replace '.' with '\.'
+    regex1="^$last_source: line ([0-9]+): (.*)\$"
+    regex2="^$last_source:([0-9]+) (.*)\$"
+
+    # FIXME: too much tricky! (delayed stderr)
+    if [[ -p /dev/stdout ]]; then
+      failure_type='SUBSHELL_TERM'
+      failure_payload="$last_error"
+
+      if [[ "$last_error" =~ $regex1 || "$last_error" =~ $regex2 ]]; then
+        failure_payload="${BASH_REMATCH[2]}"
+      fi
+      last_error="${BASH_SOURCE[1]}:${BASH_LINENO[0]} subshell term $code"
+      printf "\r" # useful!
+      kill -USR1 $$
+    else
+      failure_type='UNKNOWN'
+    fi
+
+    # debug "last_error=[$last_error] <=> ${last_source}"
+    if [[ "$last_error" =~ $regex1 || "$last_error" =~ $regex2 ]]; then
+      line=${BASH_REMATCH[1]}
+      message=${BASH_REMATCH[2]}
+      regex='^(.*): unbound variable$'
+      if [[ $code == 1 ]] && [[ "$message" =~ $regex ]]; then
+        failure_type='UNBOUND_VARIABLE'
+        failure_payload="${BASH_REMATCH[1]}"
+        stack_lines[0]=$line
+      else
+        if [[ "$message" == 'false' ]]; then
+          failure_type='FALSE'
+        else
+          regex="^return ([0-9]*) from (.*)\$"
+          if [[ "$message" =~ $regex ]]; then
+            # return_code="${BASH_REMATCH[1]}"
+            funcname="${BASH_REMATCH[2]}"
+            # >&4 echo "RETURN DETECTED line ${stack_sources[0]} $line $funcname"
+            stack_sources=("${stack_sources[0]}" "${stack_sources[@]}")
+            stack_lines=("$line" "${stack_lines[@]}")
+            stack_functions=("$funcname" "${stack_functions[@]}")
+
+            failure_type='RETURN'
+          else
+            regex='^(.*): command not found$'
+            if [[ "$message" =~ $regex ]]; then
+              failure_type='COMMAND_NOT_FOUND'
+              failure_payload="${BASH_REMATCH[1]}"
+            else
+              regex='^exit'
+              if [[ "$message" =~ $regex ]]; then
+                failure_type='EXIT'
+              else
+                regex='^(.*): No such file or directory$'
+                if [[ "$message" =~ $regex ]]; then
+                  failure_payload="${BASH_REMATCH[1]}"
+                  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 [[ $code == 127 ]]; then
+                      failure_type='FILE_NOT_FOUND'
+                      regex='\.sh$|\.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
+                  fi
+                fi
+              fi
+            fi
+          fi
+        fi
+      fi
+    else
+      failure_payload="${last_error}"
+      regex="╟─⟶"
+      if [[ "$last_error" =~ $regex ]]; then
+        last_trim=false # keep the last error for next stacktrace
+        error_block=false
+        failure_type='SUBSHELL_ERROR'
+        #
+        # >&4 echo "SUBSHELL_ERROR caught up ${BASH_SOURCE[*]} ${BASH_LINENO[*]}"
+        #
+        stack_functions[0]="${stack_functions[0]} (hint: prefer source than subshell)"
+        [[ "${code}" == 128 ]] && failure_type='SUBSHELL_SOURCE_NOT_FOUND'
+      else
+        failure_type='COMMAND_ERROR'
+      fi
+    fi
+
+    dump_failure "${last_trim:-true}" "${error_block:-true}"
+  else
+    dump_success
+  fi
+
+  # FIXME: be aware of errors during the on_exit function because it does not pop up!
+  miaou_debug "--end of on_exit => $code --"
+
+  builtin exit "$code"
+}
+
+function miaou_debug {
+  is_true "${MIAOU_DEBUG}" && >/dev/tty builtin echo -e "*********** DEBUG: $*" || true
+}
+
+function ansi_block_continuation {
+  tput sc
+  tput cuu 1
+  BG=RED FG=BLACK style_ansi "\t╦"
+  tput rc
+  FG=RED style_ansi "\t║\n"
+}
+
+function ansi_block_error {
+  FG=BLACK
+  BG=RED
+  local content detail exit_code
+
+  content=$(style_ansi "$1")
+  content=$(PADDING=2 style_padding "$content")
+
+  detail="$2"
+  [[ -n "$detail" ]] && detail=$(BG=BLACK FG=WHITE PADDING=2 style_padding "$2")
+
+  exit_code=$(FG=CYAN PADDING=2 style_padding "$3")
+  builtin echo -en "\r"
+  BLOCK_CONTINUATION_COL=5 style_block "$content$detail$exit_code"
+  ansi_reset
+  FG=RED style_ansi "     ║" && builtin echo
+}
+
+function ansi_traces {
+  local optional location sources lines functions
+  declare -n sources=$1
+  declare -n lines=$2
+  declare -n functions=$3
+  optional=false
+  for i in "${!sources[@]}"; do
+    FG=RED style_ansi "     ╟─⟶ "
+    location=$(printf "%40s" "${sources[$i]}:${lines[$i]}")
+    is_true "$optional" &&
+      location=$(FG=GRAY STYLE=ITALIC style_ansi "$location") ||
+      location=$(STYLE=ITALIC style_ansi "$location")
+    builtin echo "${location}    ${functions[$i]}"
+    optional=true
+  done
+}
+function dump_failure {
+  declare -F style_ansi >/dev/null || source "$MIAOU_BASH_DIR/lib/ansi.bash"
+  dump_stderr "${1:-true}"
+
+  local error_block="${2:-true}"
+  if is_true $error_block; then
+    miaou_debug "---error box ${failure_type:-} ---"
+    if [[ ${failure_type} == 'SUBSHELL SOURCE NOT FOUND' ]]; then
+      :
+    else
+      >&4 ansi_block_error "$failure_type" "$failure_payload" "$code"
+    fi
+    miaou_debug '---end of error box---'
+  fi
+
+  miaou_debug '---stacktrace---'
+  >&4 ansi_traces stack_sources stack_lines stack_functions
+  miaou_debug '---end of stacktrace---'
+
+  cleanup
+}
+
+function dump_stderr {
+  last_trim=${1:-false}
+  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
+  is_true "$last_trim" && unset 'tmp_error[-1]' && tmp_error=("${tmp_error[@]}")
+  if [[ "${#tmp_error[@]}" -gt 0 ]]; then
+    miaou_debug '---stderr---'
+    >&4 printf '\r'
+    for i in "${tmp_error[@]}"; do
+      >&4 echo -e "$i"
+    done
+  else
+    miaou_debug '---no stderr---'
+  fi
+}
+
+function dump_success {
+  dump_stderr
+  cleanup
+}
+
+function cleanup {
+  trap - ERR TERM EXIT DEBUG USR1
+  exec 3>&- 4>&-
+  rm "$MIAOU_BASH_ERROR"
+}
+
+# MAIN
+
+set -TEue -o pipefail
+[[ $# -lt 1 ]] && >&2 echo 'ERROR: script expected!' && builtin exit 1
+
+# trap 'on_exit $?' ERR TERM INT EXIT
+trap 'on_exit $?' ERR EXIT
+trap 'on_return' DEBUG
+trap 'on_usr1' USR1
+BASH_ARGV0="$1" && shift # to pretend script runs by itself
+
+# magic FD + delayed tee => /dev/fd/3 means delayed stderr, /dev/fd/4 remains original stderr
+exec 3> >(tee "$MIAOU_BASH_ERROR" >/dev/null) 4>/dev/stderr
+
+miaou_debug "---stdout--$$ $BASHPID $PPID--"
+# shellcheck source=/dev/null
+source "$BASH_ARGV0" 2>&3
+dump_success
diff --git a/poc b/poc
deleted file mode 100755
index 677a1c4..0000000
--- a/poc
+++ /dev/null
@@ -1,428 +0,0 @@
-#!/usr/bin/env -S -- bash
-#!/usr/bin/env -S -- bash -x
-
-# constants
-
-MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$UID")
-MIAOU_DEBUG=${MIAOU_DEBUG:-false}
-
-declare -A ANSI
-ANSI[RESET]=0
-
-ANSI[STYLE_ITALIC]=3
-ANSI[STYLE_BOLD]=1
-ANSI[STYLE_UNDERLINE]=4
-ANSI[STYLE_STRIKETHROUGH]=9
-
-ANSI[FG_BLACK]=30
-ANSI[FG_RED]=31
-ANSI[FG_GREEN]=32
-ANSI[FG_YELLOW]=33
-ANSI[FG_BLUE]=34
-ANSI[FG_PURPLE]=35
-ANSI[FG_CYAN]=36
-ANSI[FG_WHITE]=37
-ANSI[FG_GRAY]=90
-ANSI[FG_LIGHTBLUE]=94
-ANSI[FG_MAGENTA]=95
-
-ANSI[BG_BLACK]=40
-ANSI[BG_RED]=41
-ANSI[BG_GREEN]=42
-ANSI[BG_YELLOW]=43
-ANSI[BG_BLUE]=44
-ANSI[BG_PURPLE]=45
-ANSI[BG_CYAN]=46
-ANSI[BG_WHITE]=47
-ANSI[BG_GRAY]=90
-ANSI[BG_MAGENTA]=95
-
-readonly MIAOU_BASH_ERROR MIAOU_DEBUG ANSI
-
-## functions
-
-function is_true {
-  [[ "${1:-}" == '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 {
-  if is_true "${MIAOU_DEBUG}"; then
-    local i message="$*" padding=''
-    local compute_hierarchy=true
-    [[ ! -v miaou_debug_hierarchy ]] && miaou_debug_hierarchy=0
-
-    regex='^</' # starts with </
-    [[ $miaou_debug_hierarchy -gt 0 ]] &&
-      [[ "${message}" =~ $regex ]] &&
-      miaou_debug_hierarchy=$((miaou_debug_hierarchy - 1)) &&
-      compute_hierarchy=false
-
-    for ((i = 0; i < miaou_debug_hierarchy; i++)); do padding+='  '; done
-    >&4 builtin echo -e "\e[90m <== DEBUG ==> ${padding}\e[33m${message}\e[0m"
-
-    regex='[^/]>$' # does NOT end with />
-    is_true $compute_hierarchy &&
-      [[ "${message}" =~ $regex ]] &&
-      miaou_debug_hierarchy=$((miaou_debug_hierarchy + 1)) ||
-      true
-  fi
-}
-
-function on_return {
-  local regex='return ([0-9]+)'
-  if [[ "$BASH_COMMAND" =~ $regex ]] && [[ "${BASH_REMATCH[1]}" -gt 0 ]]; then
-    failure_code="${BASH_REMATCH[1]}"
-    failure_type="RETURN"
-    failure_payload="${FUNCNAME[0]}"
-    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
-function exit {
-  error_source=("${BASH_SOURCE[@]}")
-  error_lineno=("${BASH_LINENO[@]}")
-  error_funcname=("${FUNCNAME[@]}")
-  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-  unset 'error_source[0]' 'error_lineno[-1]' 'error_funcname[0]'
-  error_funcname[-1]='<main>'
-  error_source=("${error_source[@]}")
-  error_lineno=("${error_lineno[@]}")
-  error_funcname=("${error_funcname[@]}")
-
-  failure_code=${1:-0}
-  failure_type="EXIT"
-  failure_payload="${error_funcname[0]}"
-
-  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"
-}
-
-function tty_ansi {
-  local code
-  for code in "$@"; do
-    if [[ -v ANSI[$code] ]]; then
-      >&4 echo -ne "\e[${ANSI[$code]}m"
-    else
-      >&2 echo "unknown ansi key: <$code>"
-      break
-    fi
-  done
-}
-
-function print_miaou_error {
-  local source="$1" line="$2" code="$3" type="$4" payload="${5:-}"
-  local message
-  message="${source}: line ${line}: miaou_error: ${type} ${code}"
-  [[ -n "$payload" ]] && message+=" payload: ${payload}"
-  >&2 echo "$message"
-}
-
-function add_miaou_error {
-  local source="$1" line="$2" code="$3" type="$4" payload="${5:-}"
-  local message
-  message="${source}: line ${line}: miaou_error: ${type} ${code}"
-  [[ -n "$payload" ]] && message+=" payload: ${payload}"
-  tmp_error+=("$message")
-}
-
-function on_error {
-  trap - RETURN
-  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}}>"
-
-  if [[ $$ == "$BASHPID" ]]; then
-    if [[ ! -v failure_type ]]; then
-      if [[ ${BASH_COMMAND} == 'false' ]]; then
-        failure_type="FALSE"
-        print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}"
-      else
-        failure_type="COMMAND_ERROR"
-        failure_payload="${BASH_COMMAND}"
-        print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
-
-        miaou_debug "<investigate_tmp_error pid=${BASHPID}>"
-        load_tmp_error # cannot print_miaou_error after investigation
-
-        if [[ ${#tmp_error[@]} -gt 1 ]]; then
-          local last_error regex
-          last_error="${tmp_error[-2]}" # the second latest cause previous print_miaou_error above
-
-          regex='^(.*): line ([0-9]+): (.*): command not found$'
-          if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
-            failure_type='COMMAND_NOT_FOUND'
-            failure_payload="${BASH_REMATCH[3]}"
-            miaou_debug "<command_not_found payload=${failure_payload}/>"
-          else
-            regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
-            if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
-              failure_type='FILE_NOT_FOUND'
-              failure_payload="${BASH_REMATCH[3]}"
-              miaou_debug "<file_not_found payload=${failure_payload}/>"
-            fi
-          fi
-        fi
-        miaou_debug '</investigate_tmp_error>'
-      fi
-    fi
-
-    error_source=("${BASH_SOURCE[@]}")
-    error_lineno=("${BASH_LINENO[@]}")
-    error_funcname=("${FUNCNAME[@]}")
-    unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-    unset 'error_source[0]' 'error_lineno[-1]' 'error_funcname[0]'
-    error_funcname[-1]='<main>'
-    error_source=("${error_source[@]}")
-    error_lineno=("${error_lineno[@]}")
-    error_funcname=("${error_funcname[@]}")
-
-    if [[ -v failure_payload ]]; then
-      miaou_debug "</on_error exit=$failure_code type=${failure_type} payload={${failure_payload}}>"
-    else
-      miaou_debug "</on_error exit=$failure_code type=${failure_type}>"
-    fi
-    builtin exit "$failure_code"
-  else
-    print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" 'SUBSHELL_ERROR' "${BASH_COMMAND}"
-    miaou_debug "</on_error pipe=$failure_code sub_pid=$BASHPID pid=$$ command={${BASH_COMMAND}}>"
-    kill -PIPE $$
-  fi
-}
-
-function populate_error_arrays {
-
-  local source=$1 line=$2 payload=$3
-  unset 'error_source[0]' 'error_lineno[0]' 'error_funcname[0]'
-  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-  error_source=("$source" "${error_source[@]}")
-  error_lineno=("$line" "${error_lineno[@]}")
-  error_funcname=("${error_funcname[@]}" '<main>')
-}
-
-function on_pipe {
-  trap - RETURN
-  local tmp_error regex source lineno
-  miaou_debug "<on_pipe sub_pid=$BASHPID pid=$$>"
-
-  error_source=("${BASH_SOURCE[@]}")
-  error_lineno=("${BASH_LINENO[@]}")
-  error_funcname=("${FUNCNAME[@]}")
-  unset 'error_source[0]' 'error_lineno[0]' 'error_funcname[0]'
-  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
-
-  load_tmp_error
-  last_error="${tmp_error[-1]}"
-
-  regex='^(.*): line ([0-9]+): miaou_error: SUBSHELL_ERROR ([0-9]+) payload: (.*)$'
-  if [[ $last_error =~ $regex ]]; then
-    source=${BASH_REMATCH[1]}
-    lineno=${BASH_REMATCH[2]}
-    failure_code=${BASH_REMATCH[3]}
-    failure_payload=${BASH_REMATCH[4]}
-    failure_type="SUBSHELL_ERROR"
-    miaou_debug "<subshell_error payload={${failure_payload}}"
-    error_source=("$source" "${error_source[@]}")
-    error_lineno=("$lineno" "${error_lineno[@]}")
-    error_funcname=("${error_funcname[@]}" '<main>')
-  else
-    failure_code=141
-    failure_type="PIPE_ERROR"
-  fi
-  miaou_debug "</on_pipe>"
-  builtin exit "$failure_code"
-}
-
-function dump_stderr {
-  miaou_debug "<stderr count=${#tmp_error[@]}>"
-  tty_ansi FG_LIGHTBLUE
-  for i in "${tmp_error[@]}"; do echo "$i"; done
-  tty_ansi RESET
-  miaou_debug '</stderr>'
-}
-
-function dump_failure {
-  local i
-  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))
-  echo -n '╔'
-  for ((i = 0; i < length_box; i++)); do echo -n '═'; done
-  echo '╗'
-  echo -n "║ $failure_type "
-  [[ -v failure_payload ]] && echo -n ' ' && tty_ansi BG_WHITE FG_BLACK && echo -n "  $failure_payload  " && tty_ansi RESET
-  tty_ansi FG_YELLOW
-  printf "%5s" "  $failure_code  "
-  tty_ansi FG_MAGENTA
-  echo "║"
-
-  if [[ ! -v error_source ]]; then
-    echo -n '╚'
-    for ((i = 0; i < length_box; i++)); do echo -n '═'; done
-    echo '╝'
-    miaou_debug '<continuation disabled/>'
-  else
-    echo -n '╚'
-    for ((i = 0; i < 4; i++)); do echo -n '═'; done
-    echo -n '╦'
-    for ((i = 5; i < length_box; i++)); do echo -n '═'; done
-    echo '╝'
-    echo "     ║"
-    miaou_debug '<continuation enabled/>'
-  fi
-  tty_ansi RESET
-  miaou_debug '</error_box>'
-}
-
-function dump_stacktrace {
-  miaou_debug "<stacktrace count=${#error_source[@]}>"
-  local i source lineno funcname
-  for i in "${!error_source[@]}"; do
-    tty_ansi FG_MAGENTA
-    echo -n "     ╟──▷"
-    [[ $i -gt 0 ]] && tty_ansi FG_GRAY
-    tty_ansi STYLE_ITALIC
-    source="${error_source[$i]}"
-    lineno="${error_lineno[$i]}"
-    funcname="${error_funcname[$i]}"
-    printf "%40s:%.4s" "$source" "$lineno"
-    tty_ansi RESET
-    printf " \t%s" "$funcname"
-    echo
-  done
-  miaou_debug '</stacktrace>'
-}
-
-function load_tmp_error {
-  [[ -v tmp_error ]] && return 0
-
-  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
-  local count=${#tmp_error[@]}
-  if [[ $count == 0 ]]; then
-    miaou_debug "<tmp_error empty/>"
-  else
-    miaou_debug "<tmp_error count=${count}/>"
-  fi
-}
-
-function on_exit {
-  trap - RETURN
-  failure_code="${1:-0}"
-  local last_error regex
-  miaou_debug "<on_exit code=$failure_code>"
-
-  load_tmp_error
-
-  if [[ -v failure_type && "$failure_type" == 'RETURN' ]]; then
-    last_error="${tmp_error[-1]}"
-    regex='^(.*): line ([0-9]+): miaou_error: RETURN [0-9]+'
-    if [[ "$last_error" =~ $regex ]]; then
-      miaou_debug "<return code=$failure_code/>"
-      local source line
-      source="${BASH_REMATCH[1]}"
-      line="${BASH_REMATCH[2]}"
-      error_source=("$source" "${error_source[@]}")
-      error_lineno=("$line" "${error_lineno[@]}")
-      error_funcname=("$failure_payload" "${error_funcname[@]}")
-    else
-      miaou_debug "<return type=unexpected/>"
-    fi
-
-  elif [[ -v failure_type && "$failure_type" == 'COMMAND_NOT_FOUND' ]]; then
-    unset 'tmp_error[-1]' 'tmp_error[-1]'
-    add_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
-    miaou_debug '<command_not_found change_stderr />'
-
-  elif [[ -v failure_type && "$failure_type" == 'FILE_NOT_FOUND' ]]; then
-    unset 'tmp_error[-1]' 'tmp_error[-1]'
-    add_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
-    miaou_debug '<file_not_found change_stderr />'
-
-  elif [[ ! -v failure_type ]]; then
-    if [[ $failure_code -gt 0 && ${#tmp_error[@]} -gt 0 ]]; then
-      last_error="${tmp_error[-1]}"
-      miaou_debug "<investigate_tmp_error last={$last_error}>"
-
-      regex='^(.*): line ([0-9]+): (.*): unbound variable$'
-      if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
-        failure_type='UNBOUND_VARIABLE'
-        failure_payload="${BASH_REMATCH[3]}"
-        failure_code=2
-
-        local source="${BASH_REMATCH[1]}" line="${BASH_REMATCH[2]}"
-        error_source=("${BASH_SOURCE[@]}")
-        error_lineno=("${BASH_LINENO[@]}")
-        error_funcname=("${FUNCNAME[@]}")
-        populate_error_arrays "$source" "$line" "$failure_payload"
-
-        unset 'tmp_error[-1]'
-        add_miaou_error "$source" "$line" "${failure_code}" "${failure_type}" "${failure_payload}"
-        miaou_debug "<unbound_variable source=${source} line=${line} payload=${failure_payload}/>"
-      else
-        regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
-        if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
-          failure_type='SOURCE_NOT_FOUND'
-          failure_payload="${BASH_REMATCH[3]}"
-          failure_code=3
-
-          local source="${BASH_REMATCH[1]}" line="${BASH_REMATCH[2]}"
-          error_source=("${BASH_SOURCE[@]}")
-          error_lineno=("${BASH_LINENO[@]}")
-          error_funcname=("${FUNCNAME[@]}")
-          populate_error_arrays "$source" "$line" "$failure_payload"
-
-          unset 'tmp_error[-1]'
-          add_miaou_error "$source" "$line" "${failure_code}" "${failure_type}" "${failure_payload}"
-          miaou_debug "<source_not_found source=${source} line=${line} payload=${failure_payload}/>"
-        else
-          failure_type='UNKNOWN ERROR'
-          failure_payload="$BASH_COMMAND"
-        fi
-      fi
-      miaou_debug "</investigate_tmp_error>"
-    fi
-  fi
-
-  2>&3 >&3 dump_stderr
-  if [[ -v failure_type ]]; then
-    2>&3 >&4 dump_failure
-    if [[ -v error_source ]]; then
-      2>&3 >&4 dump_stacktrace
-    fi
-  fi
-  if [[ $failure_code -gt 0 ]]; then
-    miaou_debug "</on_exit code=$failure_code>"
-  else
-    miaou_debug "</on_exit success>"
-  fi
-}
-
-## main
-
-set -euo pipefail
-set -E # HALT on subshell error
-set -T # DEBUG RETURN
-
-[[ $# -lt 1 ]] && >&2 echo 'ERROR: script expected!' && builtin exit 1
-BASH_ARGV0="$1" && shift # to pretend script runs by itself
-
-trap 'on_error $?' ERR
-trap 'on_exit $?' EXIT
-trap 'on_pipe' PIPE
-trap 'on_return' RETURN
-
-if [[ -e /proc/$$/fd/3 ]]; then exec 4>&3 3>&-; else exec 4>/dev/tty; fi # swap fd 3 4 when fd 3 sent off
-exec 3>/dev/stderr 2>"$MIAOU_BASH_ERROR"
-
-miaou_debug "<source file=$BASH_ARGV0 pid=${BASHPID}/>"
-# shellcheck source=/dev/null
-source "$BASH_ARGV0"
diff --git a/test/miaou-bash-old.test.bash b/test/miaou-bash-old.test.bash
new file mode 100755
index 0000000..25b060f
--- /dev/null
+++ b/test/miaou-bash-old.test.bash
@@ -0,0 +1,83 @@
+#!/usr/bin/env bash
+
+# CONSTANTS
+
+TEST_COUNT=0
+SUCCESS_COUNT=0
+# functions
+
+function assert {
+  ((TEST_COUNT++))
+  if ./test/stub/scenario.bash "$1" >/dev/null; then
+    ((SUCCESS_COUNT++))
+  else
+    (echo "error in: $1" && exit 1)
+  fi
+
+}
+
+function strip_ansi {
+  echo "$1" | sed -E 's/\x1b\[[0-9;]*[a-zA-Z]//g'
+}
+
+function fail_type {
+  ((TEST_COUNT++))
+  local i line first error_start_above regex hint_message
+  hint_message="${3:-}"
+  mapfile -t stderr <<<"$(./test/stub/scenario.bash "$1" 2>&1 >/dev/null)"
+  # echo "stderr countains ${#stderr[@]}"
+  error_start_above=false
+  success=false
+  regex="║[[:blank:]]+([A-Z|_]+)"
+  for i in "${!stderr[@]}"; do
+    line=$(strip_ansi "${stderr[$i]}")
+    first="${line:1:1}"
+    [[ $first == ╔ ]] && error_start_above=true && continue
+    if [[ "$error_start_above" == true ]]; then
+      [[ $line =~ $regex ]] && [[ ${BASH_REMATCH[1]} == "$2" ]] && success=true
+      break
+    fi
+  done
+
+  if [[ $success == true && -n "${hint_message}" ]]; then
+    success=false
+    regex="╟─⟶.*(\(.*\))$"
+    for j in $(seq "$((i + 1))" "$((${#stderr[@]} - 1))"); do
+      line=$(strip_ansi "${stderr[$j]}")
+      if [[ $line =~ $regex ]]; then
+        [[ "${BASH_REMATCH[1]}" == "${hint_message}" ]] && success=true
+        break
+      fi
+    done
+  fi
+  if [[ $success == true ]]; then
+    ((SUCCESS_COUNT++))
+  else
+    echo "error in: $1" && return 1
+  fi
+}
+
+# main
+set -uo pipefail
+
+assert success
+fail_type subshell_term SUBSHELL_TERM
+fail_type unbound_variable UNBOUND_VARIABLE
+fail_type false FALSE
+fail_type return RETURN
+fail_type command_not_found COMMAND_NOT_FOUND
+fail_type exit EXIT
+fail_type source_not_found SOURCE_NOT_FOUND
+fail_type file_not_found FILE_NOT_FOUND
+fail_type subshell_error COMMAND_NOT_FOUND '(hint: prefer source than subshell)'
+fail_type command_error COMMAND_ERROR
+
+failed=$((TEST_COUNT - SUCCESS_COUNT))
+
+if [[ $failed -gt 0 ]]; then
+  ratio=$((100 * SUCCESS_COUNT / TEST_COUNT))
+  echo "${ratio}% passed, $SUCCESS_COUNT succeeded, $failed failed!"
+  exit 1
+else
+  echo 100% passed!
+fi
diff --git a/test/miaou-bash.test.bash b/test/miaou-bash.test.bash
index 25b060f..db510af 100755
--- a/test/miaou-bash.test.bash
+++ b/test/miaou-bash.test.bash
@@ -2,82 +2,77 @@
 
 # CONSTANTS
 
-TEST_COUNT=0
-SUCCESS_COUNT=0
 # functions
 
 function assert {
-  ((TEST_COUNT++))
-  if ./test/stub/scenario.bash "$1" >/dev/null; then
-    ((SUCCESS_COUNT++))
+  ((test_count++))
+  if miaou-bash ./test/stub/scenario.bash "$1" >/dev/null; then
+    echo -n .
   else
-    (echo "error in: $1" && exit 1)
+    echo -n F
+    failures+=("$1")
+    return 1
   fi
 
 }
 
-function strip_ansi {
-  echo "$1" | sed -E 's/\x1b\[[0-9;]*[a-zA-Z]//g'
-}
-
 function fail_type {
-  ((TEST_COUNT++))
-  local i line first error_start_above regex hint_message
-  hint_message="${3:-}"
-  mapfile -t stderr <<<"$(./test/stub/scenario.bash "$1" 2>&1 >/dev/null)"
-  # echo "stderr countains ${#stderr[@]}"
-  error_start_above=false
+  ((test_count++))
+  local success regex hint_message
   success=false
-  regex="║[[:blank:]]+([A-Z|_]+)"
-  for i in "${!stderr[@]}"; do
-    line=$(strip_ansi "${stderr[$i]}")
-    first="${line:1:1}"
-    [[ $first == ╔ ]] && error_start_above=true && continue
-    if [[ "$error_start_above" == true ]]; then
-      [[ $line =~ $regex ]] && [[ ${BASH_REMATCH[1]} == "$2" ]] && success=true
-      break
-    fi
-  done
+  hint_message="${3:-}"
+  # mapfile -t stderr <<<"$(source ./test/stub/scenario.bash "$1" 2>&1 >/dev/null 3>/dev/null)"
+  mapfile -t stderr <<<"$(miaou-bash ./test/stub/scenario.bash "$1" 2>&1 >/dev/null 3>/dev/null)"
+  last_error="${stderr[-1]}"
 
-  if [[ $success == true && -n "${hint_message}" ]]; then
-    success=false
-    regex="╟─⟶.*(\(.*\))$"
-    for j in $(seq "$((i + 1))" "$((${#stderr[@]} - 1))"); do
-      line=$(strip_ansi "${stderr[$j]}")
-      if [[ $line =~ $regex ]]; then
-        [[ "${BASH_REMATCH[1]}" == "${hint_message}" ]] && success=true
-        break
-      fi
-    done
-  fi
+  regex="^(.*): line ([0-9]+): miaou_error: $2 ([0-9]+)"
+  [[ "${last_error}" =~ $regex ]] && success=true
+
+  # if [[ $success == true && -n "${hint_message}" ]]; then
+  #   :
+  # fi
   if [[ $success == true ]]; then
-    ((SUCCESS_COUNT++))
+    echo -n .
   else
-    echo "error in: $1" && return 1
+    echo -n F
+    failures+=("$1")
+    return 1
   fi
 }
 
 # main
+
 set -uo pipefail
 
+test_count=0
+failures=()
+
 assert success
-fail_type subshell_term SUBSHELL_TERM
+fail_type subshell_term SUBSHELL_ERROR
 fail_type unbound_variable UNBOUND_VARIABLE
+fail_type unbound_associative UNBOUND_VARIABLE
 fail_type false FALSE
-fail_type return RETURN
-fail_type command_not_found COMMAND_NOT_FOUND
+fail_type last_false COMMAND_ERROR
+fail_type command_error COMMAND_ERROR
+fail_type subshell_term SUBSHELL_ERROR
 fail_type exit EXIT
+fail_type command_not_found COMMAND_NOT_FOUND
 fail_type source_not_found SOURCE_NOT_FOUND
 fail_type file_not_found FILE_NOT_FOUND
 fail_type subshell_error COMMAND_NOT_FOUND '(hint: prefer source than subshell)'
-fail_type command_error COMMAND_ERROR
 
-failed=$((TEST_COUNT - SUCCESS_COUNT))
+failed=${#failures[@]}
+success=$((test_count - failed))
 
+echo
 if [[ $failed -gt 0 ]]; then
-  ratio=$((100 * SUCCESS_COUNT / TEST_COUNT))
-  echo "${ratio}% passed, $SUCCESS_COUNT succeeded, $failed failed!"
+  ratio=$((100 * success / test_count))
+  echo "${ratio}% passed, ${test_count} tests, ${failed} failed!"
+  echo failures:
+  for failure in "${failures[@]}"; do
+    echo -e "\t- $failure"
+  done
   exit 1
 else
-  echo 100% passed!
+  echo "100% passed, ${test_count} tests"
 fi
diff --git a/test/poc.test.bash b/test/poc.test.bash
deleted file mode 100755
index f1bf4ec..0000000
--- a/test/poc.test.bash
+++ /dev/null
@@ -1,77 +0,0 @@
-#!/usr/bin/env bash
-
-# CONSTANTS
-
-# functions
-
-function assert {
-  ((test_count++))
-  if ./poc ./test/stub/scenario.bash "$1" >/dev/null; then
-    echo -n .
-  else
-    echo -n F
-    failures+=("$1")
-    return 1
-  fi
-
-}
-
-function fail_type {
-  ((test_count++))
-  local success regex hint_message
-  success=false
-  hint_message="${3:-}"
-  mapfile -t stderr <<<"$(./poc ./test/stub/scenario.bash "$1" 2>&1 >/dev/null 3>/dev/null)"
-  last_error="${stderr[-1]}"
-
-  regex="^(.*): line ([0-9]+): miaou_error: $2 ([0-9]+)"
-  [[ "${last_error}" =~ $regex ]] && success=true
-
-  # if [[ $success == true && -n "${hint_message}" ]]; then
-  #   :
-  # fi
-  if [[ $success == true ]]; then
-    echo -n .
-  else
-    echo -n F
-    failures+=("$1")
-    return 1
-  fi
-}
-
-# main
-
-set -uo pipefail
-
-test_count=0
-failures=()
-
-assert success
-fail_type subshell_term SUBSHELL_ERROR
-fail_type unbound_variable UNBOUND_VARIABLE
-fail_type unbound_associative UNBOUND_VARIABLE
-fail_type false FALSE
-fail_type last_false COMMAND_ERROR
-fail_type command_error COMMAND_ERROR
-fail_type subshell_term SUBSHELL_ERROR
-fail_type exit EXIT
-fail_type command_not_found COMMAND_NOT_FOUND
-fail_type source_not_found SOURCE_NOT_FOUND
-fail_type file_not_found FILE_NOT_FOUND
-fail_type subshell_error COMMAND_NOT_FOUND '(hint: prefer source than subshell)'
-
-failed=${#failures[@]}
-success=$((test_count - failed))
-
-echo
-if [[ $failed -gt 0 ]]; then
-  ratio=$((100 * success / test_count))
-  echo "${ratio}% passed, ${test_count} tests, ${failed} failed!"
-  echo failures:
-  for failure in "${failures[@]}"; do
-    echo -e "\t- $failure"
-  done
-  exit 1
-else
-  echo "100% passed, ${test_count} tests"
-fi