$ git reset HEAD config.pl
Unstaged changes after reset:
M       README.txt
M       config.pl
$ git status
examples/out/status_11.txt
# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   README.txt
#       modified:   config.pl
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#       setup.pl
no changes added to commit (use "git add" and/or "git commit -a")

$ git reset HEAD will reset all the files currently staged.

See also the unstage alias we created earlier.