string interpolation syntactic sugar

[Greg Ewing]

hartmut Goebel wrote:
> 
> I suppose, local() generates a new tuple. This may be quite unefficient.

A dictionary, actually.

After I posted my suggestion, it occurred to me that the unary %
operator should search both the local and global namespaces.
This could be done without creating any temporary dictionaries --
just do a normal name lookup in the current scope. It would
also give you something more than just syntactic sugar, since
this is quite awkward to express using the currently available
language features.

Greg