>>>>> "G" == GOTO Kentaro <gotoken / math.sci.hokudai.ac.jp> writes:

G> For example, loop{|a| ... } means as same as the current model.  In
G> loop{|a;b| b = a; .... }, b is a shadowed counter.

 Perhaps you can write  loop{(a;b) .... } where a and b are new local
variables in the current scope

Guy Decoux