$ git branch featurey
$ git co featurey
# edit the app.pl file , add a line, commit the change

$ git co master
# edit the app.pl file, add a line, commit the change

$ git merge featurey
Auto-merging app.pl
CONFLICT (content): Merge conflict in app.pl
Automatic merge failed; fix conflicts and then commit the result.
use 5.010;
say "config";
# some change
# adding featurx step 1
<<<<<<< HEAD
# add fix on master
# featurey 1
>>>>>>> featurey

Edit the app.pl file and resolved the conflict, removing the marks and writing the correct code.

$ git add app.pl
$ git ci -m "featurey merged"