references in environment config

Exercise-Configuration.md

@@ -342,6 +342,7 @@ Configuration for particular environments is stored here. This configuration can
 Important features:
 
 * Variable of type `file` or `file[]` in environment config can contain **wildcards**. These wildcards are then matched against files submitted in solution. For every wildcard/variable there has to be at least one file which match it.
+* Variables table in exercise environment config can contain **references** to variables which should be given during submitting of solution. Variable is reference if it starts with the character **'$'**, variable cannot be used inside variable value (textual value "hello $world", where world should be reference, is not allowed). If for some reasons is needed to use variable value which starts with dollar sign it has to be escaped with backslash, so this "\$1 million" is actual value and not a reference.
 
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