Nested finite state machines - Existing Implementations?

[Ken Robinson]

Hi All,
I have a standard which I'm implementing which calls for nested state
machines which have push and pop states and entry and exit actions.
I'm having difficulty using gen_fsm to do this. I've been looking at
plain_fsm by Ulf Wiger which looks promising. Before I reinvent the
wheel, is there any existing fully fledged nested state machines out
there?

-- 
regards,
Ken Robinson
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