Unknown variable: Gofer

Hello,

To just try out smalltalk, I installed Squeak 5.0 All-in-One: /home/edwin/squeak/Squeak-5.0-All-in-One/Squeak-5.0-All-in-One.app/Contents/Resources/Squeak5.0-15113.image

I had a small job to do where I needed to parse some data, so I wanted to install PetitParser. I copied the expression below from  the PharoBy Example book but when I try to evaluate it,  I get the error 'Unknown variable: Gofer please correct or cancel...  

Gofer new smalltalkhubUser: 'Moose' project: 'PetitParser';
package: 'ConfigurationOfPetitParser';
load.
(Smalltalk at: #ConfigurationOfPetitParser) perform: #loadDefault.

Does this mean Gofer is not installed by default?
If not, could you tell me how to install Gofer

Thanks a lot

Edwin Ancaer