If you know you will stick with these three files (people, animal, msi), it's OK; but if you think that maybe the files to check might change, or will become more, you might want to set up a table of valid filenames,

my %filenames = (
  'people.pdf' => 'People',
  'setup.msi' => 'MSI',
  # etc.
)
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In your loop, you would check whether $filename occurs in %keys %filenames, and if it does, removes it from %filenames. After the loop, you just have to print values %filenames to list the names of files which haven't been found. This will be a lot easier to maintain.