#!/usr/bin/perl
use warnings;
use strict;


my %data;

while ( <DATA> ) {

    my ( $key, $time ) = /([^\t]+\t[^\t]+)\t(.+)/ or next;

    if ( eof or not exists $data{ $key } ) {
        print join( "\t", %data ), "\n" if %data;
        %data = ( $key, $time );
        }
    else {
        $data{ $key } = join ',', $data{ $key }, $time
            unless $data{ $key } =~ /$time/;
        }
    }


__DATA__
848 05/23/06    11:00
848 05/23/06    12:30
848 05/23/06    13:00
848 05/23/06    14:00
848 05/25/06    11:00
848 05/25/06    12:00
261 05/24/06    11:00
261 05/24/06    12:30
261 05/24/06    13:00
261 05/24/06    13:00
261 05/24/06    13:00
261 05/24/06    13:00