PurposeUses the Groovy JDK join method to concatenate the toString() representation of each item in this collection with the given separator.
That would result in output like this:
<g:join in="['Grails', 'Groovy', 'Gradle']" delimiter="_"/>
in- The collection to iterate over
delimiter(optional) - The value of the delimiter to use during the join. If no delimiter is specified then ", " (a comma followed by a space) will be used as the delimiter.