Open up your text editor and make demo.reb:
Rebol [
Title: {Lemme show ya somethin'}
]
data: [a b c]
print [line of data]
print [file of data]
There are tools in the making for connecting dynamic structure back to its source. And they're being accounted for. But, there's a really hard problem here.
Almost every programming language which involves abstractions (e.g. macros) gets screwed in terms of connecting what the runtime processes and can understand (the expanded macro) vs. what was written (the instantiation, e.g. "source").
Mapping backwards from a projection is a challenge. This may be amusing:
I'm open to ideas here, but... the thing is, this is non-trivial.
See: The Law of Leaky Abstractions (Spolsky)