use strict;
use warnings;

use Benchmark qw(cmpthese);

my @numbers;
push @numbers, int rand 1e9 for 1 .. 1000;

my $rcUseCdarke = sub
   {
       my $res = useCdarke($_) for @numbers;
   };

my $rcUseFAQ = sub
   {
       my $res = useFAQ($_) for @numbers;
   };

my $rcUseMolt = sub
   {
       my $res = useMolt($_) for @numbers;
   };

my $rcUsePrefUN = sub
   {
       my $res = usePrefUN($_) for @numbers;
   };

my $rcUseJwkrahn = sub
   {
       my $res = useJwkrahn($_) for @numbers;
   };

my $rcUseSplit = sub
   {
       my $res = useSplit($_) for @numbers;
   };

my $rcUseSubstr = sub
   {
       my $res = useSubstr($_) for @numbers;
   };

cmpthese (50,
   {
      Cdarke => $rcUseCdarke,
      FAQ => $rcUseFAQ,
      Jwkrahn => $rcUseJwkrahn,
      Molt => $rcUseMolt,
      PrefUN => $rcUsePrefUN,
      Split => $rcUseSplit,
      Substr => $rcUseSubstr
   });

sub useCdarke
{
    my $number = reverse shift;
    $number =~ s/(\d{3})/$1,/g;
    $number = reverse $number;
    return $number;
}

sub useFAQ
{
    my $number = reverse shift;
    $number =~
       s/(^[-+]?\d+?(?=(?>(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g;
    return $number;
}

sub useJwkrahn
{
    return scalar reverse join ',', unpack '(a3)*', reverse shift;
}

sub useMolt
{
    my $number = shift;
    while ($number =~ s/(\d)(\d\d\d)(?!\d)/$1,$2/) {};
    return $number;
}

sub usePrefUN
{
    my $num = reverse shift;
    my @threes = $num =~ /(.{1,3})/g;
    return scalar reverse join ',', @threes;
}

sub useSplit
{
    my $ct = 0;
    my $len = length $_[0];
    return join q{},
       reverse map
       {
           ++ $ct % 3
              ? $_
              : $ct == $len
                 ? $_
                 : ($_, q{,})
       }
       reverse split m{}, $_[0];
}

sub useSubstr
{
    my $number = shift;
    my $offset = -3;
    while (abs $offset < length $number)
    {
        substr $number, $offset , 0, q{,};
        $offset -= 4;
    }
    return $number;
}