Is calling Regex "Regexp" a Javascript thing or am I missing something?
It's the name of the constructor, for example:
const pat1 = new RegExp(`42//?5`)
So, I used that in the book name.
They're both alternate spellings of the same thing. Yes JS/ES/Ruby and a few other languages use "RegExp" in their standard libraries. Henry Spencer referred to one of his regex libraries as "regexp" as far back as 1986. I prefer regex because that's what I learned first, and it's easier to say "regexes" when you want to pluralize it, but I've seen both forms pop up over the years.
/regexp?/