replace runs of four leading spaces with tabs in .m files

spaces-to-tabs.sh

#!/bin/bash

# Bah. I prefer spaces. So why this script? I was on a project that required tabs.

export isconfirmed=$1

if [[ ! "$isconfirmed" == 'confirmed' ]]; then
    echo 'run with a "confirmed" command line argument to confirm you want to run this destructive operation'
    exit -1
fi

find . -type f -name "*.m" -print | xargs perl -pi -e "1 while s/\G {4}/\t/gc;" {} \;