Implemented doRepeat block

Please fix my lousy Elixir.
Line 440 may be too ugly. Initially I thought I could do "|> &{&1, repeat_loop_var}" which seemed like a really clever way to return a tuple without breaking the pipe chain but the need for the dot for the anonymous function call got me again, in this case you actually need a .(). In addition, since . has precedence over & you need an extra set of parens.