You can shave a few points off of your substr sub by taking the abs and length functions out of the loop: 
sub useSubstr
{
    my $number = shift;
    my $length = -( 1 + length $number );
    my $offset = -3;
    while ( $offset > $length )
    {
        substr $number, $offset, 0, q{,};
        $offset -= 4;
    }
    return $number;
}

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In reply to Re^2: Formatting a number by jwkrahn
in thread Formatting a number by harryf

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