[disclaimer: this post is sure to demonstrate my ignorance of regular expressions & substitutions]

I'd already seen vroom's Q&A node about adding commas to a number, but it seemed there ought to be an easier way. I thought that a regexp like this one would do the trick:
$number=1234567; # with commas, should be "1,234,567"
$number=~s/(\d)(\d{3})\b/$1\,$2/g;

[download]
However, this code will actually change $number to 1234,567. Despite the "g" on the end of the regexp, it still sort of works from beginning-to-end, so it only inserts the comma at the end.
Then I thought, "well, I could do this once for each comma" which would work like this: 
while($number=~s/(\d)(\d{3})\b/$1\,$2/g){
 # nothing here -- how silly is this?
}

[download]
So then, obviously, the while loop continues as long as the substitution was successful. But is this terribly silly? Could my same code be modified slightly to work correctly with ONE simple substitution? Or am I simply better off using vroom's sub at the aforementioned node?

In reply to regexp for adding commas to a number by Kozz

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