modal verb + HAVE BEEN BEING + past participle – English Grammar Profiler
It is extremely rare to have 5 verbs in a row in English. For this reason, we think this modal verb + perfect progressive passive structure is a C2 marker.
A search in the NOW corpus for:
_VM _VH been being _VVN
1 MIGHT HAVE BEEN BEING RELEASED 3 2 MAY HAVE BEEN BEING HELD 2 3 SHOULD’VE BEEN BEING REPLACED 2 4 SHOULD’VE BEEN BEING EXECUTED 1 5 MUST HAVE BEEN BEING BULLIED 1 6 MUST HAVE BEEN BEING BROUGHT 1 7 MUST HAVE BEEN BEING BETRAYED 1 8 MIGHT HAVE BEEN BEING TOLD 1 9 MIGHT HAVE BEEN BEING SMUGGLED 1 10 WOULD HAVE BEEN BEING WHISPERED 1 11 WOULD HAVE BEEN BEING USED 1 12 WOULD HAVE BEEN BEING TIED 1 13 WOULD HAVE BEEN BEING CELEBRATED 1 14 WOULD HAVE BEEN BEING ATTACKED 1
15 WILL HAVE BEEN BEING DEVELOPED 1
