tree parser input:  ( do i ( * a b ) ( * d a ) )
ast_scan("#( DO %1:Var %2:. %3:. )") results: found 3 successful matches
loop_var: i
lower_bound: ( * a b ) ( * d a )
upper_bound: ( * d a )
tree parser output:  ( do i ( * a b ) ( * d a ) )
