ack2 design

Here we try to document ack's design, including design decisions that have already been made, so that we don't keep rehashing them.

Design choices that are inviolate.

ack will not do replacing of text. It is not a replacement for sed.
ack will only use core Perl modules and File::Next. No other modules may be required.
ack must be able to be built as a single-file standalone file.
ack must be cross-platform. Specifically, it must run on Windows.

Design questions that have been investigated

Would ack be faster if we used the integer pragma?

It seems not. Brian M. Carlson investigated this and reported his findings here: beyondgrep#398

There seemed to be no effect.