I've got a little something, should only be two lines of code maximum.
Make a commatizer with regsub that uses no identifiers other than maybe a $+, and the input $1.
So 12345678.123456 will be turned into: 12,345,678.123456
It's not really that helpful for others as you can script it without regsub, but when I was offered to make it as a challenge, I quite enjoyed it.
Good luck.
