int outer_API_bar()
{
   // Modify internal state
   internal_foo()
}

int internal_foo()
{
  // Do stuff

  if (internal_state_variable)
  {
     // Do some more stuff
     internal_state_variable = false;
  }
}

int outer_API_bar()
{
   // Modify internal state

   internal_foo(internal_state_variable)

   // This could be another function if repeated many
   // times in the module
   if (internal_state_variable)
   {
      internal_state_variable = false;
   }
}

int internal_foo(bool arg)
{
  // Do stuff

  if (arg)
  {
     // Do some more stuff
  }
}