#!/usr/bin/perl

use strict;
use warnings;

my $str = "123456";

$_ = $str;
1 while s/(\d)(\d)(\d)/$3$2/;
print "$_\n";

$_ = $str;
1 while s/(\d)(\d)(\d)/$3$2/g;
print "$_\n";
__END__
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