Sorry for the vagary. I don't have specifics. But yes, lines of code, not line of data from a file. I haven't seen the code (yet). I don't think it'll be due to iterating through a hash. He's too good not to consider that. The STDERR vs STDOUT sound like a real possibility, one that I'll keep in mind. I saw something like this years ago when working with Perl/Tk. Correct if wrong, but that would be multi-threaded, interrupt driven thing where synching may not be as simple as observing what lines of code come before others. Good ideas, thanks for the input. Will add to this if/when I get code. Reducing the script down to the bare bones that still demos the behavior is a good idea. Done that sort of thing before, good strategy.