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block->forward
block ->forward: any ...
When a block object is forwarded, it will bind the arguments to the var objects in block<-parameters by position. Possible exceeding arguments are bound to @arg1 ... for compatibility reasons. Next the block is code->execute’d just like the and object.

Example: 

?- send(chain(chain(a,b), chain(c,d)), for_all,
                block(new(Sub, var),
                          message(Sub, for_all,
                          message(@pce, write_ln, Sub, @arg1)))).
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