Including external files

[Daniel Winterstein]

I quite often find myself making documents that pull together other
fragmentary documents. Does anyone have suggestions for an include or
embed syntax? I.e. a way of saying "pull in the contents of document X
here". Has this been implemented before?
Such a syntax might be:
(embed: snippet.txt)
or
[include](snippet.txt)

Your thoughts?

Best regards,
 - Daniel