#!/usr/bin/perl -w
use strict;
my %result;
for my $row(<DATA>) {
    my($num,$date,$time)=split /\s+/,$row;
    push @{ $result{$num}->{$date} }, $time;
}
for my $num(sort keys %result) {
    for my $date(sort keys %{$result{$num}}) {
        my %contains;
        my @time_ary;
        for my $time(sort @{$result{$num}->{$date}} ){
            push @time_ary, $time unless $contains{$time}++;
        }
        printf "%s\t%s\t%s\n", $num,$date,join(',',@time_ary);
    }
}
__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