use strict ; use warnings ;

  foreach my $t (1234567, 123.4567, -123456, .123456, '.1234567', -10**1000) {
    printf "%12s -> oko1:%12s, faq:%12s\n", $t, commify($t), commify_faq($t) ;
  } ;

  sub commify {
    my ($s) = @_ ;
    my @list = () ;
    my $c = 0 ;
    for (reverse split //, $s){
      unshift @list, $c++ % 3 || $c == 1 ? $_ : "$_,";
    } ;

    return join '', @list ;
  } ;

  sub commify_faq {
    local $_  = shift ;
    1 while s/^([-+]?\d+)(\d{3})/$1,$2/ ;
    return $_ ;
  } ;