#!/usr/bin/env perl
use warnings;
use strict;
use diagnostics -traceonly;
use autodie;
open FOO, '<', '/tmp/foo/' or die "ACK! $!";
__END__
Uncaught exception from user code:
  Can't open '/tmp/foo/' for reading: 'No such file or directory' at - line 6
  main::__ANON__("FOO", "<", "/tmp/foo/") called at - line 6

##</code><code>##

{
  no autodie qw(open);          # open failures won't die
  open(my $fh, "<", $filename); # Could fail silently!
  # ^^^ add your "or die" to this open
}