SYNOPSIS
	string process_string(string str)

DESCRIPTION
	Searches string <str> for occurences of a "value by function call",
	which is @@ followed by an implicit function call. See
	"value_by_function_call" in the principles section.

	The value should contain a string like this:
	@@function[:filename][|arg|arg]@@

	Note that process_string does not recurse over returned
	replacement values. If a function returns another function
	description, that description will not be replaced.

SEE ALSO
	value_by_function_call(P), notify_fail(E), communication(P)
