Gleam replace regex match

regexp.gleam

import gleam/io
import gleam/list
import gleam/option.{Some}
import gleam/regex.{type Match, type Regex}
import gleam/string

pub fn replace_match(
  each pattern: Regex,
  in string: String,
  with substitute: fn(Match) -> String,
) -> String {
  let matches = regex.scan(pattern, string)
  let replacements = list.map(matches, fn(m) { #(m.content, substitute(m)) })

  list.fold(replacements, string, fn(acc, replacement) {
    let #(p, s) = replacement
    string.replace(acc, p, s)
  })
}

const input = "
@('hello')
@('world')
"

pub fn main() {
  let assert Ok(re) = regex.from_string("@\\('([^']*)'\\)")
  replace(each: re, in: input, with: substitute)
  |> io.println
  //
  // HELLO
  // WORLD
  //
}

fn substitute(match: Match) -> String {
  let assert [Some(s)] = match.submatches
  string.uppercase(s)
}