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sub hanoi { my ($disks, $start, $end, $via) = @_; ... hanoi($disks-1, $via, $end, $start) ); }
sub iter_hanoi { my ($disks, $start, $end, $via) = @_; ... return $rval; } }
sub iter_choose_n { my $n = pop; ... return $rval; } }