[antlr-interest] Evaluating exprs+

[Ilia Kantor]

I have a rule 
exprs returns [String value]: expr+;

Thanks to Terrence and ANTLR3, it works.

How can I concatenate all values returned by expr ?

Something like
exprs returns [String value]: a b { return a+b };
but for antlr3 and working in my case.