asterisk users - Nov 2005 - command returns a result code of -1 (indicating failure)

In the wiki it states:
> When an extension is dialed, the command tagged with a priority of 1 is
> executed, followed by command priority 2, and so on. This goes on until:
>
> the call is hung up,
> a command returns a result code of -1 (indicating failure),
> a command with the next higher priority doesn't exist (note: Asterisk
> will not "skip over" missing priorities), or  the call is routed
to a new
> extension.

In the case of a return code of -1, where do we go when a -1 is 
encountered? How can I retain control?

For instance, on a Read, if the user enters nothing, I need to continue 
execution in a known state.