#!/usr/bin/env miaou-bash

function f1 {
  if [[ -v nested_count ]]; then
    >/dev/tty echo already defined $nested_count
    ((nested_count++))
  else
    >/dev/tty echo brand new
    nested_count=1
  fi
  echo $nested_count
}

echo "v=$(f1)"
echo "v=$(f1)"
echo "v=$(f1)"
f1
f1
echo $nested_count