You could specify in the EXPRESSION property a Boolean expression and the REDIRECT tag will become conditional, which means that the redirection will be executed if and only if the Boolean expression evaluates to true.
DOC
Specify in the DOC property the document that will be displayed instead of the actual one. This property is primarily intended for DBSP documents.
URL
Specify in the DOC property a document that is outside of the current site or server. If this property is specified, the redirection will act as an HTML redirect.
Note: All the code interpreted before the REDIRECT tag will be discarded and substituted by the content located in the new page. However, all the database modifications made with the DATASET or QRYEXEC tag before the redirection will not be discarded (in the database context, will not be rolled back).