Corion...even though you didn't have the code needed to test, you did solve my problem...Vielen Dank! I now run a "dynamic" require within each thread...and all is well:

# we have the artifact here, it's verified so we just need to parse it
sub parse_artifact()
{
        my ($format, $file) =@_;
        my $t_line;
        my @args = undef;

        # this thread's scope needs to re-load the file-specific input
+ module
        my @temp = split(/::/, $format->{'name'});
        my $formatInput = $temp[2] . ".pm";
        my $thread_format_dir = Log2t::Common::get_directory();
        $thread_format_dir .= '/Log2t/input/';

        require  $thread_format_dir . '/' . $formatInput;
[download]

I am seeing ~25% speed increases on my test machine already...thanks for your help