[exim] acl endpass

I have an acl and I want to conditionally delegate annother ACL to
decide

 acl_foo:
    accept
       condition = ${if bool:{$acl_m_something}}
       endpass
       acl = acl_bar
    accept    
       condition = ${if bool:{$acl_m_something_else}}
    deny

The spec says that endpass is not needed, what's the alternative way to
write that?
acl_bar could return anything (drop,deny,defer,discard,accept etc.)

Is there a way that preserves the message set by acl_bar ?

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