amb=. ([ , ' ' , ])&>/&.>@:((({:@:[ = {.@:])&>/&> # ])@:,@:({@(,&<)))
   >@(amb&.>/) ('the';'that';'a');('frog';'elephant';'thing');('walked';'treaded';'grows');(<'slowly';'quickly')
+-----------------------+
|that thing grows slowly|
+-----------------------+