[Txr-users] Syntax change.

[Kaz Kylheku]

Hi All,

I'm making a change to the syntax. @(block)'s will be terminated by 
@(end),
enclosing their own scope, rather than sharing the surrounding scope.

This makes more sense and makes blocks more useful and easier to use.

Blocks are useful now even without their termination feature
being used. Example: unnamed block used to limit the scope of
skip's search.

@; skip until just those three lines match, not the entire
@; rest of the query. When they match, move past the block
@; and process the rest of the query independently of the skip
@(block)
@(skip)
ma
te
rial
@(end)

Skip out of the block, and move on to
material following the block:

@(block foo)
...
...
@(accept foo)
...
@(end)

Blocks can be used to control backtracking behavior.
I.e. you can assert "if we match this thing here, we
can succeed and not look for other ways to match",
and this is done by means means of aborting out of some
enclosing block via @(accept) to continue after that block.