diff --git a/lib/bashrc_watcher.sh b/lib/bashrc_watcher.sh
new file mode 100644
index 0000000..82939ef
--- /dev/null
+++ b/lib/bashrc_watcher.sh
@@ -0,0 +1,86 @@
+function sed_replace {
+  REGEX=$1
+  STRING=$2
+  FILE=$3
+  if ! grep -Eq "$REGEX" "$FILE"; then
+    builtin echo -e "$STRING" >>"$FILE"
+    echo 'appended'
+  else
+    sed -Ei "s|$REGEX|$STRING|g" "$FILE"
+    echo 'replaced'
+  fi
+}
+
+function bashrc_count_lines {
+  wc -l "$HOME/.bashrc" | cut -d' ' -f1
+}
+
+function bashrc_watch_start {
+  if [[ -z "${BASHRC_LINES+set}" ]]; then
+    BASHRC_LINES=$(bashrc_count_lines)
+  else
+    BASHRC_EVOLVED=true
+  fi
+}
+
+function bashrc_watch_end {
+  bashrc_lines=$(bashrc_count_lines)
+  if [[ "$BASHRC_LINES" -lt "$bashrc_lines" || -n "${BASHRC_EVOLVED+set}" ]]; then
+    echo
+    echo '*****************************'
+    echo '* BASHRC has evolved!       *'
+    echo '* please synchronize:       *'
+    echo '*                           *'
+    echo "*   source ~/.bashrc        *"
+    echo '*                           *'
+    echo '*****************************'
+    echo
+  fi
+}
+
+function _bashrc_env_with_prefix {
+  arg1="$1"
+  arg2="$2"
+  prefix="$3"
+  if printenv | grep -q "$arg1"; then
+    real_value=$(eval "echo \$$arg1")
+    echo "success for $arg1 = $real_value"
+  else
+    case "$prefix" in
+    export)
+      session_line="export ${arg1}=${arg2}"
+      regex="$session_line"
+      ;;
+    eval)
+      session_line="eval \"\$($arg2)\""
+      regex="eval \"\\\$\\($arg2\\)\""
+      ;;
+    *) echo "unknown prefix $prefix" && exit 10 ;;
+    esac
+    sed_replace "$regex" "$session_line" "$HOME/.bashrc" &>/dev/null
+    eval "$session_line"
+    set +e
+    trap - EXIT
+    eval "BASHRC_LINES=$BASHRC_LINES $0"
+    exit $?
+  fi
+
+}
+
+function bashrc_export {
+  _bashrc_env_with_prefix "$1" "$2" 'export'
+}
+
+function bashrc_eval {
+  _bashrc_env_with_prefix "$1" "$2" 'eval'
+}
+
+function on_exit() {
+  rv=$?
+  # [[ $rv -eq 0 ]] && bashrc_watch_end
+  bashrc_watch_end
+  exit $rv
+}
+
+bashrc_watch_start
+trap "on_exit" EXIT
diff --git a/main b/main
index 450d026..8e53d6e 100755
--- a/main
+++ b/main
@@ -1,81 +1,9 @@
 #!/usr/bin/env bash
 
-# global variables
-
-# functions
-
-function bashrc_count_lines {
-    wc -l "$HOME/.bashrc" | cut -d' ' -f1
-}
-
-function bashrc_watch_start {
-    if [[ -z "${BASHRC_LINES+set}" ]]; then
-        BASHRC_LINES=$(bashrc_count_lines)
-    else
-        BASHRC_EVOLVED=true
-    fi
-}
-
-function bashrc_watch_end {
-    bashrc_lines=$(bashrc_count_lines)
-    if [[ "$BASHRC_LINES" -lt "$bashrc_lines" || -n "${BASHRC_EVOLVED+set}" ]]; then
-        echo
-        echo '*****************************'
-        echo '* BASHRC has evolved!       *'
-        echo '* please synchronize:       *'
-        echo '*                           *'
-        echo "*   source ~/.bashrc        *"
-        echo '*                           *'
-        echo '*****************************'
-        echo
-    fi
-}
-
-function _bashrc_env_with_prefix {
-    arg1="$1"
-    arg2="$2"
-    prefix="$3"
-    if printenv | grep -q "$arg1"; then
-        real_value=$(eval "echo \$$arg1")
-        echo "success for $arg1 = $real_value"
-    else
-        case "$prefix" in
-        export)
-            session_line="export ${arg1}=${arg2}"
-            regex="$session_line"
-            ;;
-        eval)
-            session_line="eval \"\$($arg2)\""
-            regex="eval \"\\\$\\($arg2\\)\""
-            ;;
-        *) echo "unknown prefix $prefix" && exit 10 ;;
-        esac
-        append_or_replace "$regex" "$session_line" "$HOME/.bashrc" &>/dev/null
-        eval "$session_line"
-        set +e
-        eval "BASHRC_LINES=$BASHRC_LINES $0"
-        exit $?
-    fi
-
-}
-
-function bashrc_env_export {
-    _bashrc_env_with_prefix "$1" "$2" 'export'
-}
-
-function bashrc_env_eval {
-    _bashrc_env_with_prefix "$1" "$2" 'eval'
-}
-
-# main
-
 set -Eeu
-bashrc_watch_start
+source "$(dirname "$0")/lib/bashrc_watcher.sh"
 
 echo 'init'
-bashrc_env_export 'SESSION_RESTART' true
-bashrc_env_export 'TOTO' fluo
-bashrc_env_eval 'MISE_SHELL' "$HOME/.local/bin/mise activate bash"
+bashrc_eval 'MISE_SHELL' "$HOME/.local/bin/mise activate bash"
+bashrc_export 'TOTO' fluo
 echo 'end'
-
-bashrc_watch_end