Hi, there.
Command prefixes will never execute on their own, and that is by design. Command prefixes require command suffixes in order to make a command that will execute. You'll want to take a look at VoiceAttack's documentation on composite (prefix/suffix) commands. Search for 'Command Type' within the 'Command Screen' section - it provides a fair amount of detail on what composite commands are all about, as well as their requirements.
Another useful topic in the help documentation is 'Dynamic Command Sections'. This will also help create many variations on single command with a little bit of added syntax. Press F1 while VoiceAttack is in focus to bring up the help document.
If you provide a little bit of context on what it is you're trying to do, there may be a simple way to go about it. Just let us know here.
Hope that helps!