my @built;
my @files = get_files_to_build();
for (@files) {
    my $built = build_file($_);
    unless ($built) {
        warn "Could not build $_!\n";
        next;
    }
    my $filename = File::Spec->catfile($path, $_);
    open(OUTPUT, "> " . $filename) or die "Can't open $filename: $!";
    print OUTPUT $built;
    push @built, [ $filename, $_ ];
}

my $ftp = Net::FTP->new($remotehost, Debug => 1)
    or die "Can't connect to $remotehost: $@\n";
$ftp->login($username, $password)
    or die "Couldn't authenticate!\n";
$ftp->cwd('www');

foreach my $updated (@built) {
    my ($location, $name) = @$updated;
    $ftp->put($name, $location) or warn "Couldn't put $name: $@\n";
}

$ftp->quit();
[download]

There are I came up with four possible solutions. One is very easy, the second works implicitly. The third may not work on every platform, and the fourth is crazy.

I'm including a couple of hints in HTML comments. I know several saints who would pick this out right off the bat, but let's leave this for people who don't normally speak up.

Hints follow.

Update: So far, ZZamboni and Albannach have both caught it. Good job! arturo also got it right, pointing out a legitimate typo that wasn't the bug. Then Spudnuts sent me a /msg, and I decided it would be okay for people to post their own answers. It might be good to stick them in HTML comments (<!-- comment here -->), though. So far no one's provided anything but the first and most direct fix.

tilly spotted two other typos and came up with four fixes. Abigail also gets a gold star, but if either of those two are novices, I'm secretly Jon Orwant.