open doesn't normally die on errors, so actually, your exception handling kind of is working ;-)

Looks to me like you might be using a combination of diagnostics and autodie:

#!/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
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If you don't want open to die and you want to handle the error yourself, you can lexically disable autodie, as shown in its synopsis:

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