The problem is that /-o will also match something like --my-irrelevant-option.

Word boundaries match the end (or the beginning) of the word.

How exactly to do it depends on the regex library, my less is built with PCRE2 therefore I can do /-o\b.

It depends on how the document is written, but \> stops matching on a period, comma, apostrophe, space, newline, what have you. Word boundary matching is just very handy.

As to why its that set of characters.... Honestly I have no idea :) Regexes are just what they are and I assume the special escape made sense to the inventor at least.

Also curious what trouble OP was having. Wouldn’t a trailing space be enough?

Dealing with multiple more complex tools the last few days, looking the short option up, because i needed to know what it does, was about a hundred steps through walls of text. Then came the yay and curl manpages; one or two steps. That's when i wrote the post.