#!/usr/bin/env perl -l

use strict;
use warnings;
use autodie;

use constant {
    UNIQ   => 0,
    CODE   => 2,
    JOINER => ':',
};

my %data;

while (<DATA>) {
    my @cols = split;

    if (exists $data{$cols[UNIQ]}) {
        $data{$cols[UNIQ]}->[CODE] .= JOINER . $cols[CODE];
    }   
    else {
        $data{$cols[UNIQ]} = [ @cols ];
    }   
}   

print "@{$data{$_}}" for sort keys %data;

__DATA__
A1 text1 NY Jan 01
A2 text2 LN Feb 02
A3 text3 SG Mar 03
A2 text2 NY Feb 02
A1 text1 SG Jan 01
A1 text1 AUS Jan 01

##</code><code>##

A1 text1 NY:SG:AUS Jan 01
A2 text2 LN:NY Feb 02
A3 text3 SG Mar 03