问SVN::Error回调如何识别调用它的上下文？

EN

#
# This part is the library that implements error handling a bit like
# SVN::Client
#
sub default_error_handler {
  croak "An error occurred: $_[0]";
}

our $global_error_handler = \&default_error_handler;

sub library_function_that_might_fail {
  &$global_error_handler("Guess what - it failed!");
}

#
# This part is the function that wants to detect an error
#
sub do_lots_of_stuff {
  my $error = undef; # No errors so far!

  local($global_error_handler) = sub { $error = $_[0]; };

  library_function_that_might_fail();
  library_function_that_might_fail();
  library_function_that_might_fail();

  if ($error) {
    print "There was an error: $error\n";
  }
}


#
# Main program
#
do_lots_of_stuff();