An alternative way of writing an `if` statement and then referencing the same value is to use `with` instead. `with` rebinds the context (`.`) within its scope and skips the block if the variable is absent, unset or empty.
The set of *empty* values is defined by [the Go templates package](https://golang.org/pkg/text/template/). Empty values include `false`, the number zero, and the empty string.
If you want to render a block if an index or key is present in a slice, array, channel or map, regardless of whether the value is empty, you should use [`isset`](/functions/isset) instead.
The following example checks for a [user-defined site variable](/variables/site/) called `twitteruser`. If the key-value is not set, the following will render nothing:
