diff --git a/admin-guide/puppet/hiera.md b/admin-guide/puppet/hiera.md
index b0c26cad..e4455f07 100644
--- a/admin-guide/puppet/hiera.md
+++ b/admin-guide/puppet/hiera.md
@@ -125,3 +125,12 @@ block: >
 ```
 
 and place either the string or the block at the required place in your Hiera YAML.
+
+# Hiera Variable Interpolation
+
+Within Hiera also variable interpolation might be use to include other Hiera keys or facts, etc. into the values.
+For details check out the [Puppet documentation](https://www.puppet.com/docs/puppet/7/hiera_merging.html#interpolation_functions)
+
+As such an interpolation starts with `%{`, some key or file content (especially in Apache configuration) might be interpreted as variable interpolation and result in some part of the text disappear.
+Or it might simply the puppet run with `Syntax error in string` if Puppet fails to parse what it considers an interpolation.
+To escape a `%` you can write `%{literal('%')}` instead.