Luau utility for string.split behavior with support for more than one delimiter

multi_split.luau

-- jonbyte, 2026

local function split(
	input: string, -- string to be split
	sep: { string }, -- array of separator strings
	include: true? -- if separators should be included in result
)
	if #sep == 0 then
		-- early exit: there is nothing to split the string
		return { input }
	end

	local result: { string } = {}
	local len = #input
	local i = 1

	repeat

		local k = 0 -- offset to exclude first character of found separator from plain substring
		local w = 0 -- 0-based width of separator string if found
		local j = len -- upper bound of substring
		local s: string? -- separator string if found on this pass

		for _, v in sep do
			local a, b = string.find(input, v, i, true)
			if a and a <= j then
				s = v -- the separator string
				j = a
				w = b - a -- we add 1 later
				k = -1
			end
		end

		local sub = string.sub(input, i, j+k)
		table.insert(result, sub)

		if include and s then
			table.insert(result, s)
		end

		i = j + w + 1

	until s == nil

	return result
end