{text="
chapter one
chapter two
chapter three
chapter four
chapter five
chapter six
chapter seven
chapter eight
chapter nine
chapter ten"}
{=extractregex(text, "(chapter[\D\S]+)")}
In the above snippet, I would like the regex to start from an nth instance of the word "chapter". For example, start from the 6th "chapter", giving me:
chapter six
chapter seven
chapter eight
chapter nine
chapter ten
Thanks 
This is something that is more suitable to handle as a list.
First convert the string to a list via the split() function and then extract the relevant part of the list with the slice() function.
For example:
{text="chapter one
chapter two
chapter three
chapter four
chapter five
chapter six
chapter seven
chapter eight
chapter nine
chapter ten"}
{=slice(split(text, "\n"), 6)}
You can also join the resulting list back together into a string:
{=join(slice(split(text, "\n"), 6), "\n")}
Ok, I should've clarified. These would be headings of a text. Between each of them, there would be paragraphs of text.
So:
{text="
chapter one
[bunch of text]
chapter two
[bunch of text]
chapter three
[bunch of text]
chapter four
[bunch of text]
chapter five
[bunch of text]
chapter six
[bunch of text]
chapter seven
[bunch of text]
chapter eight
[bunch of text]
chapter nine
[bunch of text]
chapter ten
[bunch of text]
"}
{=extractregex(text, "(chapter[\D\S]+)")}
I want to be able to extract regex from a specific chapter to another specific chapter e.g. from chapter 6 to chapter 8.
Any ideas?
This is actually pretty ugly from a regular expression side, but it can be done.
Regular expressions support a "{n}" syntax to specify you should match the preceding expression n times.
You'll also need to use the "(?:)" syntax which defines a non-capture group that doesn't return its results from the function:
So in your example we could do something like:
{text="
chapter one
[bunch of text]
chapter two
[bunch of text]
chapter three
[bunch of text]
chapter four
[bunch of text]
chapter five
[bunch of text]
chapter six
[bunch of text]
chapter seven
[bunch of text]
chapter eight
[bunch of text]
chapter nine
[bunch of text]
chapter ten
[bunch of text]
"}
{=extractregex(text, "(?:(?:chapter[\s\S]+?){5})((?:chapter[\s\S]+?){3})(chapter|$)")}
Great stuff. So I've made some additional changes now, to allow me to use a formtext to define at what point I want to start and end.
{text="
chapter one
[bunch of text]
chapter two
[bunch of text]
chapter three
[bunch of text]
chapter four
[bunch of text]
chapter five
[bunch of text]
chapter six
[bunch of text]
chapter seven
[bunch of text]
chapter eight
[bunch of text]
chapter nine
[bunch of text]
chapter ten
[bunch of text]
"}
Start at Chapter {formtext: name=start; default=1}
End at Chapter {formtext: name=end; default=10}
{n1=start-1 if start <> "" else 0}
{n2=end-n1 if end <> "" else 10}
{=extractregex(text, "(?:(?:chapter[\s\S]+?){"&n1&"})((?:chapter[\s\S]+?){"&n2&"})(chapter|$)")}
nice!
I learned from the best 