perl pie but only act on git files. Optional second parameter can dramatically speed up the replacement.

git-pie

#!/bin/bash

set -euo pipefail

###
# Usage
#
# git pie <perl-script> [git grep options]


script=$1; shift
# if no grep options, search for `.` which will return all files.
[ $# = 0 ] && set -- .

# -z support files with weird characters/spaces
# -I don't search binary files
git grep --name-only -z -I "$@" | xargs -0 perl -pi -e "$script"