Re: RFC 104 (v1) Backtracking

[Damian Conway]

   > As I understand things:
   > 
   >    BLOCK1 andthen BLOCK2
   > 
   > evaluates BLOCK1 and then if BLOCK1 evaluates to "true" evaluates
   > BLOCK2.  If BLOCK2 evaluates to "true" we're done.  If BLOCK2
   > evaluates to "false", then BLOCK1 is re-evaluated. 

So how is that different from:

        do BLOCK1 until do BLOCK2

???