thanks!

i just didnt know how to use x properly, got a little confused reading the doc.
i added x1 to the format string wherever i wanted to ignore a character

    my $count = 0;
    foreach my $len (@lens)
    {
        if ( $count ++ ) 
        {
            $format .= "x1";
        }
        $format .= "A$len";
    }
[download]

does the deed nicely