No subject

in Python expressions (they might always appear in string literals, of
course, but that's easy enough to avoid):

	@ # $ : ; ?

Any of these can be used for delimiting expressions within a certain
construct.  As for delimiting the start of the construct itself, any
character can be used following the prefix (by default, @), except for
those already used by the system.

As you point out, ! would be a bad choice since it appears legally in
Python code.  (This discussion also made me just realize that @<... :
...> for try/catch like behavior with expressions was a mistake, since >
can appear perfectly legally in expressions ... no matter, I can
collapse it all into an uber-@( ... ) syntax.)

What would you suggest? @: ... : ... :?  It's something I would expect
only advanced users to need, so it's probably not a problem if it
doesn't look too pretty.

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
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 A lambda calculus explorer in Python.