FROM_OK_FILE_BUT_MISSING: {
    my $warn_called;
    local $SIG{__WARN__} = sub { $warn_called = 1 };
 
    my $tempfile = File::Temp->new;
    File::Copy::copy('t/filelist.txt', $tempfile);
    print {$tempfile} "t/non-existent-file.txt\n";
    $tempfile->close;
    ...
}