$number =~ s/(^\D*\d{1,3}(?=(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g;

##</code><code>##

s/(^[-+]?\d+?(?=(?>(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g;