>If you have to verify that something had the right result, then
>verify the result itself

Hmm.. perl doesn't make this easy though.

open() returns undef on failure, that's it.

Now that's not terribly useful - I have to treat a non-existant file separately to other errors, so I either have to check $! or test -f without introducing a race condition.

Ok, so I could go to something like this:

  use Errno;

  unless ( open(INFILE, "<", $filename) )
  {
    return if exists &Errno::ENOENT && $! + 0 == &Errno::ENOENT;
    return unless -f $filename;

    die "open failed: $!";
  }

Not great, but more portable. Makes use of Errno::ENOENT if its available but fallbacks to a simple -f as a last resort.

So, any suggestions for improvements???