Reuse 'do' keyword instead of hash sign (#)

[Patrick Viry]

> The introduction of 'assert' caused enough pain and in that case the
> existing uses must surely have been related to assertions. Many existing
> uses of lambda will be unrelated to the replacement use.

It shouldn't have been painful. There are ways to parse non-reserved
keywords, we do this all the time at Ateji with our language
extensions. You just need to make sure that the grammar is designed so
that the context can eliminate ambiguities between identifier and
keyword. This is probably the case for 'assert', not sure about
'lambda'.

Patrick
Just a note, I'm not advocating any syntax design.