You might work on a feature or a bug-fix, sometimes you will need to stop working and implement some other changes. There might be several people working on different features at the same time. Git allows and encourages frequent commits

$ git branch
* master

$ git branch featurex
$ git branch
  featurex
* master

$ git checkout featurex
Switched to branch 'featurex'
$ git branch
* featurex
  master

make some changes to app.pl, and commit them to the repository

Check using gitk