You're one of the few people to actually have been sued under the DMCA, as I understand it, so you have better grounds than most to be cautious.

It's strange, if you really think about it, what it means to extract lines from a file. What if you make a copy of the file minus those lines? The lines are still there in the original file. But this would surely be infringing if just editing the file would be, right?

And then, how about your perl script, which extracts individual lines from the file, but not the magic 8? That amounts to much the same thing as making a copy of the file minus the 8 lines, except that you're also removing some more lines.

And what kind of protection do these 8 lines provide? You can still read the file, albeit with some difficulty. You can make copies of the file, post it to the net, share with your friends, right? There is nothing in the file text which says differently. Maybe these magic 8 lines don't rise even to the very low threshold of an effective copyright protection measure as defined by the DMCA, given that the text is still readable by unaided humans.

Not sued (yet?!). Won a DMCA exemption by demonstrating the reasonable likelihood of being sued (doesn't help against half a dozen other laws though).

There's an aspect of the DMCA (1201(c)(3)) where there's no mandate for any particular processing for controls, no "broadcast flag":

"Nothing in this section shall require that the design of, or
design and selection of parts and components for, a consumer
electronics, telecommunications, or computing product provide for
a response to any particular technological measure, so long as
such part or component, or the product in which such part or
component is integrated, does not otherwise fall within the
prohibitions of subsection (a)(2) or (b)(1)."

So the question is whether one is circumventing (forbidden) or not responding (allowed).

There could be a very interesting legal case in this situation. Given the past history of Adobe, I am not eager to be it :-)