I have a small preference for requiring 'end', just for consistency with the statement version.
I would argue that it is inconsistent with the Lua-wide convention that the "end" keyword terminates a block of statements, never an _expression_.
Lua's grammar is designed in such a way that the end of an _expression_ can almost always(*) be determined without an explicit termination keyword. This is BTW what makes most syntax extension proposals messy and/or ambiguous and/or alien feeling.
(*) the only exception I can think of, and which doesn't feel right IMO, is the fact that "foo(bar)(gnu)(gnat)" is understood differently from "foo(bar)\n(gnu)(gnat)".
