Remove or replace Nth capture

remove_replace_Nth_capture.lua

function remove_replace_Nth_capture(src_str,capt,N,repl_str) 
-- if the last arg is omitted or isn't a string then works for removal
-- 1. if not N then N is 1
-- 2. if no captures or N is 0 or greater than the number of captures returns original string
local N = N and tonumber(N) and math.abs(math.floor(N)) -- validate N
	if not N then N = 1 end
local repl_str = repl_str and type(repl_str) == 'string' and repl_str
local cntr = 0
local str_new = ''
	for w1, w2 in src_str:gmatch('(%w*)([%p%s%c]*)') do
	cntr = (N ~= cntr and w1 == capt or N == cntr) and cntr+1 or cntr
		if repl_str then 
			if N == cntr then w1, w2 = repl_str..w2, '' end
		str_new = str_new..w1..w2
		elseif N ~= cntr then 
		str_new = str_new..w1..w2
		end
	end
return str_new, str ~= str_new -- 2nd val is boolean showing if any changes were made
end