#!/usr/bin/perl -ps
# This one is a small improvement of the code that adds commas
#   to numbers. It has the advantage of not breaking tabular
#   format (such as the output of `ls` and `du`)
# Adopted from Perl Monks "How do I add commas to a number?"
#
# Use -r switch to cancel the alignment
#
# Example: ls -l | ,

unless($r) { while (s/\s (?=\d)/ 0/g) {} }
$_=reverse;
s/(\d\d\d)(?=\d)(?!\d*\.)/$1,/g;
$_=scalar reverse;
unless($r) { while (s/\s[0,](?=[\d,])/  /g) {} }