...
            $people = 1 if ($filename eq 'people.pdf');
            $animal = 1 if ($filename eq 'animal.pdf');
            $msi    = 1 if ($filename eq 'setup.msi');
        }
    }
    print "People not found\n"   unless defined $people;
    print "animal not found\n"   unless defined $animal;
    print "MSI file not found\n" unless defined $msi;
...

##</code><code>##

my %filenames = (
                 people.pdf => 'Person',
                 animal.pdf => 'animal',
                 setup.msi  => 'MSI file',
                );
...
            for (keys %filenames) {
                delete $filenames{$_} if $filename eq $_;
            }
        }
    }
    for (values %filenames) {
        print "$_ not found\n";
    }
...