#!/usr/bin/env perl foreach $arg (0..$#ARGV) { my $num = int($ARGV[$arg]); my $fmt = "", $cnt = 0; while($num > 0) { $fmt = ($num % 10) . $fmt; if(++$cnt % 3 == 0 and $num >= 10) { $fmt = "," . $fmt; } use integer; $num /= 10; } print "$fmt\n"; }