use strict;
use warnings;

my %cols;
my $ctr=0;
my @data = map {/(.*),(.*), (.*)/; $2."\t"x($cols{"\t$3"}//=++$ctr)."$1\n" } <DATA>;
print sort {$cols{$a}<=>$cols{$b}} keys %cols;
print "\n", @data;

__DATA__
52,1427766557, bob
12,1427766556, bob
5,1427766555, bill
10,1427766554, joe
23,1427766553, bob