I really like the advice from "Perl Best Practices" to code in paragraphs. Sometimes, a large function cannot be broken up usefully, because a lot of state needs to be shared between the different parts, or because the parts don't have a meaning outside of the very specific algorithm.

In that case, code in paragraphs: Split the function body into multiple steps, put a blank line between these and, most importantly, add a comment at the start of the paragraph that summarizes its purpose.

Now when someone else finds your function, they can just gloss over the paragraph headings to get an idea of the function's overall structure, then drill down into the parts that are relevant for them.