in reply to How do I print a large integer with thousands separators?

for ( $number )
{
  /\./
    ? s/(?<=\d)(?=(\d{3})+(?:\.))/,/g
    : s/(?<=\d)(?=(\d{3})+(?!\d))/,/g;
}

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This says if the number has a decimal point, end there for the purposes of commafication. Otherwise, go to the end of the string.

In Section Seekers of Perl Wisdom