This will show examples on how to use the Grails collect tag(<g:collect>). This tag is similar to each tag and it iterates over each element of a collection. The difference is the added attribute expr.
The Grails unless tag (<g:unless>) renders it's body when the condition given is false. It is the opposite of the if tag that renders a body when the condition is true. This will show a simple example on how to use this tag.
The Grails while tag (<g:while>) can be used to render GSP section multiple times. It behaves similar to the while loop in Java/Groovy but just translated to a GSP tag. This will show a simple example on how to use this tag.