Hi hello_beginner,

I agree with hippo, this question is very similar to join column 3 for unique values. In fact, a few changes to the code I posted in Re: join column 3 for unique values gives the results that you require.

If you have your data in data.txt

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
[download]

This script,

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Table;

my $t = Data::Table::fromCSV('data.txt', 0, undef,{delimiter => ' '});
my $mt = $t->melt(['col1', 'col2', 'col4', 'col5']);
my $ct = $mt->cast(['col1', 'col2', 'col4', 'col5'], 'variable', Data:
+:Table::STRING, 'value', \&col_join);

$ct->sort('col1', 1, 0);
$ct->reorder( [ 'col1', 'col2', 'col3', 'col4', 'col5' ] );

print $ct->csv(0, {delimiter => " "});

exit;

sub col_join {
    my @data = @_;
    my $joined = join(":", @data);
    return($joined);
}
[download]

will give this output

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

If you often work on problems like these, I recommend reading Data::Table and the Data::Table Cookbook (especially Section 8.1: Reshaping - melting and casting for table statistics).

As mentioned by stevieb, please take a closer look at How do I post a question effectively? especially the Select an informative title section.