[NTG-context] Example of passing unexpanded text between \startfoo ... \stopfoo into Lua?

Hi Hans and others, I've been searching the mailing list and source code for one or more examples of passing unexpanded text appearing between a \startfoo ... \stopfoo block into Lua, but without luck. Is there such an example you could point me to? A colleague and I are experimenting with strategies to implement a literate programming module for ConTeXt, and we'd like to have something like \startcodeblock[language=c,file=foo.c, etc.][blockname] // This is the main routine... int main() { return 0; } \stopcodeblock We would appreciate any thoughts you have about how to implement such a module. Thanks, Kevin