Hello spudulike, and welcome to the Monastery!

Your first line, $line = pack ("A1170") ;, fills $line with a string of 1170 spaces. The next line, substr ($line, 0, 135) = " " ;, replaces the first 135 characters of $line with a single space, thereby shortening the string by 134 characters. Similarly, the next-to-last line shortens the string by a further 506 characters! What are those two lines intended to do?

I think you need to study the documentation for the substr function. :-)

Hope that helps,