understanding lpeg.Cmt recursively

matchTime.lua

local success = function(all, pos) print('success') return pos end

local fail = function(all, pos) print('fail') return pos end

local common = Cmt(P('['), success)*(V('STMP')^0)*P(']')

local main_cmt = common + Cmt(P(']'),fail)

local main_normal = common + P(']')/fail

local grammer_cmt = P({'STMP', STMP = main_cmt })

local grammer_normal = P({'STMP', STMP = main_normal })

local str = '[[]]'

---------------------------------------------------------------
grammer_cmt:match(str)

-- success
-- success
-- fail
-- fail

-- QUESTION: why does the second pattern ( printing fail ) match ?? 

---------------------------------------------------------------
grammer_normal:match(str)

-- success
-- success

-- This seems to work as expected

@spc476 do you know why Cmt match all inner Cmt when used recursively ?

Thanks !