recursion confusion

[Jon Schull]

Sometimes recursion befuddles me.  This is one of those times.

I want to convert a graph structure into a nested string 
For example I want this...

g={0:[], 1:[11], 2:[21,  22], 22:[221,222]}

...to become this
	"0, 	1[11], 2 [21,  22[221, 222]] "

(with 221 and 222 nested under 22 which is also nested under 2)

Of course, I want this to work for arbitrary nesting, and for strings
as well as numbers.

(Why? in order to create graphviz "record" shapes.)

I suspect there are concise recursive, and not-so-concise
understandable, ways to do this.  I'd be grateful for either, but
would prefer the latter.

Thanks very much...