doc: adds alternative variable syntax using @ delimiters to the documentation
diff --git a/src/site/apt/examples/filter.apt b/src/site/apt/examples/filter.apt
index b42b746..f663696 100644
--- a/src/site/apt/examples/filter.apt
+++ b/src/site/apt/examples/filter.apt
@@ -29,7 +29,7 @@
Filtering
Variables can be included in your resources. These variables, denoted by the
- <<<$\{...\}>>> delimiters, can come from the system properties, your project
+ <<<$\{...\}>>> or <<<@...@>>> delimiters, can come from the system properties, your project
properties, from your filter resources and from the command line.
For example, if we have a resource <<<src/main/resources/hello.txt>>> containing
