irb(main):015:0> a = {b: {c: {d: 1}}}
=> {:b=>{:c=>{:d=>1}}}
irb(main):016:0>  b = [ :b, :c, :d ]
=> [:b, :c, :d]
irb(main):017:0> c = a ; c = c[v] while ( v = ( b.any? ? b.shift : false ) )
=> nil
irb(main):018:0> c
=> 1
irb(main):019:0>